Data & Methodology — Marquette County

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

Contaminant Data — All Analytes

47 well testing events on record, covering 20 analytes. Data spans 1973 to 2025.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. WI Avg
Nitrate 42 1973–2015 93%
45% of limit ↑ 168% above
Arsenic 23 2002–2023 96%
2% of limit ↓ 87% below
Chloride 43 1973–2023 98%
4% of limit ~ typical
Fluoride 43 1973–2023 49%
2% of limit ↓ 63% below
HFPO-DA (GenX) 3 2022 0%
— —
Iron 43 1973–2023 44%
4% of limit ↓ 98% below
Lead 25 1976–2023 36%
1% of limit ~ typical
Manganese 43 1973–2023 63%
2% of limit ↓ 99% below
Nitrite 40 1975–2015 15%
1% of limit ~ typical
PFHxS 3 2022 0%
— —
PFNA 3 2022 0%
— —
PFOA 3 2022 100%
6% of limit ↓ 62% below
PFOS 3 2022 0%
— —
Radon 5 1995–2003 100%
6% of limit ↓ 64% below
Sulfate 43 1973–2023 100%
4% of limit ↓ 38% below
Uranium 28 1994–2023 86%
0% of limit ↓ 86% below
Hardness 43 1973–2023 100%
— ~ typical
PFBS 3 2022 33%
— ↑ 125% above
pH 45 1973–2023 100%
— ~ typical
Sodium 43 1973–2023 100%
— ↓ 61% 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 WI.

Compare your result with Marquette County

Of the 23 arsenic tests on record for Marquette County (2002–2023), 4% found none, and half were below 0.2 µg/L.

Of the 43 chloride tests on record for Marquette County (1973–2023), 2% found none, and half were below 8.71 mg/L.

Of the 43 fluoride tests on record for Marquette County (1973–2023), 51% found none.

Of the 43 iron tests on record for Marquette County (1973–2023), 56% found none.

Of the 25 lead tests on record for Marquette County (1976–2023), 64% found none.

Of the 43 manganese tests on record for Marquette County (1973–2023), 37% found none, and half were below 0.26 µg/L.

Of the 42 nitrate tests on record for Marquette County (1973–2015), 7% found none, and half were below 4.04 mg/L.

Of the 43 sulfate tests on record for Marquette County (1973–2023), 0% found none, and half were below 11 mg/L.

Of the 28 uranium tests on record for Marquette County (1994–2023), 14% found none, and half were below 92 ng/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Nitrate 42 samples
  • Arsenic 23 samples
  • Chloride 43 samples
  • Fluoride 43 samples
  • Iron 43 samples
  • Lead 25 samples
  • Manganese 43 samples
  • Nitrite 40 samples
  • Sulfate 43 samples
  • Uranium 28 samples
  • Hardness 43 samples
  • pH 45 samples
  • Sodium 43 samples

Limited data (<15 samples) — interpret with caution

  • HFPO-DA (GenX) 3 samples
  • PFHxS 3 samples
  • PFNA 3 samples
  • PFOA 3 samples
  • PFOS 3 samples
  • Radon 5 samples
  • PFBS 3 samples

CDC Health Outcome Correlations

Where contaminants detected in Marquette 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 Marquette County Prevalence WI Average Source Year
Nitrate Cancer prevalence 6.0% 7.0% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Marquette 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 WI with at least one sample for that analyte.

Last updated: 2026-07-15

Full methodology →