Data & Methodology — Watonwan County

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

Contaminant Data — All Analytes

69 well testing events on record, covering 19 analytes. Data spans 1964 to 2024.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. MN Avg
Iron 35 1964–2016 97%
1052% of limit ↑ 47% above
Manganese 25 1964–1993 100%
460% of limit ~ typical
PFOS municipal 8 2023 75%
200% of limit ~ typical
Sulfate 39 1964–2016 100%
78% of limit ↑ 312% above
PFOA municipal 6 2023 67%
3856% of limit ↑ 797% above
PFHxS municipal 4 2023 50%
255% of limit ↑ 219% above
Arsenic 24 1980–2009 88%
51% of limit ↓ 41% below
Lead 24 1980–2009 71%
60% of limit ↑ 35% above
Nitrate 35 1964–2009 86%
0% of limit ↓ 98% below
Chloride 56 1964–2025 100%
3% of limit ↓ 60% below
Fluoride 33 1964–2009 97%
7% of limit ~ typical
HFPO-DA (GenX) municipal 2 2023 0%
— —
Nitrite 14 1980–2009 14%
1% of limit ↓ 57% below
PFNA municipal 3 2023 33%
20% of limit ~ typical
Uranium 1 1980 0%
— —
Hardness 17 1964–1981 100%
— ↑ 116% above
PFBS municipal 4 2023 50%
— ↑ 31% above
pH 19 1964–1994 100%
— ~ typical
Sodium 35 1964–2016 100%
— ↑ 35% 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 Watonwan County

Of the 24 arsenic tests on record for Watonwan County (1980–2009), 12% found none, and half were below 2.13 µg/L.

Of the 56 chloride tests on record for Watonwan County (1964–2025), 0% found none, and half were below 7.7 mg/L.

Of the 33 fluoride tests on record for Watonwan County (1964–2009), 3% found none, and half were below 290 µg/L.

Of the 35 iron tests on record for Watonwan County (1964–2016), 3% found none, and half were below 3.13 mg/L.

Of the 24 lead tests on record for Watonwan County (1980–2009), 29% found none, and half were below 3.46 µg/L.

Of the 25 manganese tests on record for Watonwan County (1964–1993), 0% found none, and half were below 230 µg/L.

Of the 35 nitrate tests on record for Watonwan County (1964–2009), 14% found none, and half were below 40 µg/L.

Of the 39 sulfate tests on record for Watonwan County (1964–2016), 0% found none, and half were below 195 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Iron 35 samples
  • Manganese 25 samples
  • Sulfate 39 samples
  • Arsenic 24 samples
  • Lead 24 samples
  • Nitrate 35 samples
  • Chloride 56 samples
  • Fluoride 33 samples
  • Hardness 17 samples
  • pH 19 samples
  • Sodium 35 samples

Limited data (<15 samples) — interpret with caution

  • PFOS 8 samples
  • PFOA 6 samples
  • PFHxS 4 samples
  • Nitrite 14 samples
  • PFNA 3 samples
  • Uranium 1 sample
  • PFBS 4 samples

Public vs. Private Water in Watonwan County

13 Active public water systems
8,836 Residents on public water
17% Households on private wells

Public water systems in Watonwan 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 Watonwan 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 Watonwan County Prevalence MN Average Source Year
Arsenic Cancer prevalence 7.9% 7.0% 2020
Arsenic Kidney disease rate 3.6% 2.9% 2020
Lead Heart disease rate 6.0% 6.6% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Watonwan 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

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