Data & Sources — St. Clair County

How we built the St. Clair County well water report: sample counts, data sources, and confidence tiers.

Sample Summary

59361 total samples analyzed for St. Clair County. Data spans 1960 to 2018.

Confidence Tiers

Data Sources

This report aggregates data from the following public databases:

Methodology

Raw records are normalized to µg/L, deduplicated by sample ID, and filtered to remove certified outliers. Analyte names are mapped to EPA canonical forms. See the full methodology page for details.

Last updated: 2026-05-08