Data & Methodology — Grand Traverse County

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

Contaminant Data — All Analytes

13695 total samples analyzed across 20 analytes. Data spans 1967 to 2023.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. MI Avg
Iron 34 1976–1986 97%
47% of limit ↓ 76% below
Arsenic 5 1982–2013 100%
20% of limit ↓ 38% below
Lead 45 1985–2013 100%
1% of limit ↓ 95% below
PFNA municipal 14 2023–2025 0%
0% of limit —
PFHxS municipal 14 2023–2025 0%
0% of limit —
PFOS municipal 14 2023–2025 0%
0% of limit —
PFOA municipal 14 2023–2025 0%
0% of limit —
HFPO-DA (GenX) municipal 14 2023–2025 0%
0% of limit —
Chloride 61 1967–2023 100%
2% of limit ↓ 80% below
Fluoride 6 1982–1986 83%
8% of limit ~ typical
Nitrite 26 1999–2015 77%
0% of limit ↓ 74% below
Uranium 3 1978–1987 100%
0% of limit ↓ 56% below
Radon 2 1991 100%
12% of limit ↓ 64% below
Nitrate 34 1999–2013 100%
2% of limit ↓ 56% below
Sulfate 45 1967–2003 98%
2% of limit ↓ 87% below
Manganese 2 1977–1978 50%
20% of limit ↓ 85% below
pH 13 1967–2013 100% — — ↓ 22% below
PFBS municipal 14 2023–2025 14%
— —
E. coli 1 2010 0%
— —
Sodium 39 1977–2023 100% — — ↓ 80% 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 MI.

Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Iron 34 samples
  • Lead 45 samples
  • Chloride 61 samples
  • Nitrite 26 samples
  • Nitrate 34 samples
  • Sulfate 45 samples
  • Sodium 39 samples

Limited data (<15 samples) — interpret with caution

  • Arsenic 5 samples
  • PFNA 14 samples
  • PFOA 14 samples
  • Fluoride 6 samples
  • Uranium 3 samples
  • Radon 2 samples
  • Manganese 2 samples
  • pH 13 samples
  • E. coli 1 sample

Public vs. Private Water in Grand Traverse County

180 Active public water systems
57,994 Residents on public water
39% Households on private wells

Public water systems in Grand Traverse 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 Grand Traverse 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 Grand Traverse County Prevalence MI Average Source Year
Lead Heart disease rate 7.2% 7.4% 2020
Arsenic Cancer prevalence 8.0% 7.2% 2023
Lead Heart disease rate 5.1% 7.4% 2023
Arsenic Cancer prevalence 8.1% 7.2% 2020
Arsenic Kidney disease rate 3.1% 3.2% 2020

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

Last updated: 2026-05-27

Full methodology →