Data & Methodology — Chisago County

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

Contaminant Data — All Analytes

224 well testing events on record, covering 20 analytes. Data spans 1967 to 2024.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. MN Avg
Radon 1 2014 100%
140% of limit ↑ 170% above
Manganese 52 1967–2025 90%
195% of limit ↓ 60% below
Iron 143 1967–2025 90%
24% of limit ↓ 97% below
PFOA municipal 33 2007–2025 21%
55% of limit ↓ 87% below
Chloride 191 1967–2025 100%
2% of limit ↓ 68% below
PFOS municipal 28 2023–2025 14%
134% of limit ↓ 33% below
Arsenic 118 1978–2025 31%
30% of limit ↓ 65% below
PFHxS municipal 26 2023–2025 15%
25% of limit ↓ 69% below
Lead 118 1978–2025 6%
29% of limit ↓ 34% below
Fluoride 122 1967–2025 93%
5% of limit ↓ 32% below
HFPO-DA (GenX) municipal 24 2023–2025 0%
— —
Nitrate 106 1967–2011 73%
0% of limit ↓ 99% below
Nitrite 91 2010–2011 4%
0% of limit ↓ 76% below
PFNA municipal 28 2007–2025 0%
— —
Sulfate 162 1967–2025 98%
3% of limit ↓ 84% below
Uranium 83 2010–2014 34%
4% of limit ~ typical
Sodium 140 1967–2025 100%
— ↓ 83% below
pH 47 1967–2015 100%
— ~ typical
PFBS municipal 26 2023–2025 15%
— ↓ 57% below
Hardness 16 1967–2014 100%
— ↓ 57% 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 Chisago County

Of the 118 arsenic tests on record for Chisago County (1978–2025), 69% found none.

Of the 191 chloride tests on record for Chisago County (1967–2025), 0% found none, and half were below 6.08 mg/L.

Of the 122 fluoride tests on record for Chisago County (1967–2025), 7% found none, and half were below 176 µg/L.

Of the 143 iron tests on record for Chisago County (1967–2025), 10% found none, and half were below 50 µg/L.

Of the 118 lead tests on record for Chisago County (1978–2025), 94% found none.

Of the 52 manganese tests on record for Chisago County (1967–2025), 10% found none, and half were below 95.9 µg/L.

Of the 106 nitrate tests on record for Chisago County (1967–2011), 27% found none, and half were below 8 µg/L.

Of the 162 sulfate tests on record for Chisago County (1967–2025), 2% found none, and half were below 7.38 mg/L.

Of the 83 uranium tests on record for Chisago County (2010–2014), 66% found none.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 52 samples
  • Iron 143 samples
  • PFOA 33 samples
  • Chloride 191 samples
  • PFOS 28 samples
  • Arsenic 118 samples
  • PFHxS 26 samples
  • Lead 118 samples
  • Fluoride 122 samples
  • HFPO-DA (GenX) 24 samples
  • Nitrate 106 samples
  • Nitrite 91 samples
  • PFNA 28 samples
  • Sulfate 162 samples
  • Uranium 83 samples
  • Sodium 140 samples
  • pH 47 samples
  • PFBS 26 samples
  • Hardness 16 samples

Limited data (<15 samples) — interpret with caution

  • Radon 1 sample

Public vs. Private Water in Chisago County

110 Active public water systems
40,925 Residents on public water
51% Households on private wells

Public water systems in Chisago 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 Chisago 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 Chisago County Prevalence MN Average Source Year
Arsenic Cancer prevalence 6.1% 7.0% 2020
Arsenic Kidney disease rate 2.4% 2.9% 2020
Lead Heart disease rate 6.4% 6.6% 2020

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