Data & Sources — Washtenaw County

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

Sample Summary

99783 total samples analyzed for Washtenaw County. Data spans 1884 to 2016.

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