Data & Methodology — Clearwater County

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

Contaminant Data — All Analytes

84 well testing events on record, covering 18 analytes. Data spans 1962 to 2024.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. MN Avg
Manganese 39 1966–2025 51%
133% of limit ↓ 73% below
Radon 4 1993–1995 100%
9% of limit ↓ 83% below
Iron 53 1966–2025 66%
11% of limit ↓ 98% below
Arsenic 43 1987–2025 35%
40% of limit ↓ 53% below
Lead 46 1987–2025 9%
3% of limit ↓ 94% below
Chloride 72 1966–2025 100%
1% of limit ↓ 87% below
Fluoride 55 1966–2025 73%
5% of limit ↓ 28% below
HFPO-DA (GenX) 4 2024–2025 0%
— —
Nitrate 24 1966–2011 50%
6% of limit ↓ 75% below
Nitrite 15 1991–2011 13%
0% of limit ↓ 71% below
PFNA 4 2024–2025 0%
— —
PFOA 4 2024–2025 0%
— —
PFOS 4 2024–2025 0%
— —
Sulfate 72 1966–2025 96%
2% of limit ↓ 89% below
Uranium 4 1993–1995 0%
— —
Sodium 71 1966–2025 100%
— ↓ 88% below
pH 52 1966–2014 100%
— ~ typical
Hardness 41 1966–2011 100%
— ~ typical

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 Clearwater County

Of the 43 arsenic tests on record for Clearwater County (1987–2025), 65% found none.

Of the 72 chloride tests on record for Clearwater County (1966–2025), 0% found none, and half were below 2.46 mg/L.

Of the 55 fluoride tests on record for Clearwater County (1966–2025), 27% found none, and half were below 150 µg/L.

Of the 53 iron tests on record for Clearwater County (1966–2025), 34% found none, and half were below 18 µg/L.

Of the 46 lead tests on record for Clearwater County (1987–2025), 91% found none.

Of the 39 manganese tests on record for Clearwater County (1966–2025), 49% found none, and half were below 1 µg/L.

Of the 24 nitrate tests on record for Clearwater County (1966–2011), 50% found none.

Of the 72 sulfate tests on record for Clearwater County (1966–2025), 4% found none, and half were below 4.89 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 39 samples
  • Iron 53 samples
  • Arsenic 43 samples
  • Lead 46 samples
  • Chloride 72 samples
  • Fluoride 55 samples
  • Nitrate 24 samples
  • Nitrite 15 samples
  • Sulfate 72 samples
  • Sodium 71 samples
  • pH 52 samples
  • Hardness 41 samples

Limited data (<15 samples) — interpret with caution

  • Radon 4 samples
  • HFPO-DA (GenX) 4 samples
  • PFNA 4 samples
  • PFOA 4 samples
  • PFOS 4 samples
  • Uranium 4 samples

Public vs. Private Water in Clearwater County

29 Active public water systems
3,978 Residents on public water
75% Households on private wells

Public water systems in Clearwater 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 Clearwater 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 Clearwater County Prevalence MN Average Source Year
Arsenic Cancer prevalence 6.1% 7.0% 2020
Arsenic Kidney disease rate 2.9% 2.9% 2020
Lead Heart disease rate 9.0% 6.6% 2020

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