Data & Methodology — Cass County

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

Contaminant Data — All Analytes

367 well testing events on record, covering 19 analytes. Data spans 1962 to 2024.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. MN Avg
Manganese 305 1965–2025 74%
314% of limit ↓ 36% below
Iron 321 1965–2025 69%
186% of limit ↓ 74% below
PFOA 34 2022–2025 56%
74% of limit ↓ 83% below
PFOS 29 2024–2025 45%
32% of limit ↓ 84% below
Arsenic 251 1987–2025 58%
17% of limit ↓ 81% below
Chloride 323 1965–2025 89%
1% of limit ↓ 91% below
Fluoride 231 1965–2025 77%
3% of limit ↓ 57% below
HFPO-DA (GenX) 20 2022–2025 0%
— —
Lead 251 1987–2025 16%
4% of limit ↓ 92% below
Nitrate 40 1965–2011 50%
2% of limit ↓ 94% below
Nitrite 13 1991–2011 0%
— —
PFHxS 2 — 100%
95% of limit ~ typical
PFNA 28 2022–2025 32%
4% of limit ↓ 79% below
Sulfate 323 1965–2025 86%
2% of limit ↓ 89% below
Uranium 7 2001–2011 100%
0% of limit ↓ 90% below
Sodium 326 1965–2025 100%
— ↓ 87% below
pH 86 1965–2012 100%
— ~ typical
PFBS 3 — 100%
— ↓ 75% below
Hardness 75 1965–2011 100%
— ↓ 39% below

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 Cass County

Of the 251 arsenic tests on record for Cass County (1987–2025), 42% found none, and half were below 0.428 µg/L.

Of the 323 chloride tests on record for Cass County (1965–2025), 11% found none, and half were below 1.32 mg/L.

Of the 231 fluoride tests on record for Cass County (1965–2025), 23% found none, and half were below 100 µg/L.

Of the 321 iron tests on record for Cass County (1965–2025), 31% found none, and half were below 78 µg/L.

Of the 251 lead tests on record for Cass County (1987–2025), 84% found none.

Of the 305 manganese tests on record for Cass County (1965–2025), 26% found none, and half were below 96 µg/L.

Of the 40 nitrate tests on record for Cass County (1965–2011), 50% found none.

Of the 34 pfoa tests on record for Cass County (2022–2025), 44% found none, and half were below 0.531 ng/L.

Of the 29 pfos tests on record for Cass County (2024–2025), 55% found none.

Of the 323 sulfate tests on record for Cass County (1965–2025), 14% found none, and half were below 4.23 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 305 samples
  • Iron 321 samples
  • PFOA 34 samples
  • PFOS 29 samples
  • Arsenic 251 samples
  • Chloride 323 samples
  • Fluoride 231 samples
  • HFPO-DA (GenX) 20 samples
  • Lead 251 samples
  • Nitrate 40 samples
  • PFNA 28 samples
  • Sulfate 323 samples
  • Sodium 326 samples
  • pH 86 samples
  • Hardness 75 samples

Limited data (<15 samples) — interpret with caution

  • Nitrite 13 samples
  • PFHxS 2 samples
  • Uranium 7 samples
  • PFBS 3 samples

Public vs. Private Water in Cass County

255 Active public water systems
24,774 Residents on public water
86% Households on private wells

Public water systems in Cass 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 Cass 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 Cass County Prevalence MN Average Source Year
Arsenic Cancer prevalence 6.1% 7.0% 2020
Arsenic Kidney disease rate 2.8% 2.9% 2020
Lead Heart disease rate 9.4% 6.6% 2020

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