Interactive map
Monitoring patterns by state
Color reflects unique eligible community water systems with complete monitoring. It is not a population exposure or compliance map.
EPA UCMR 5 (2023–2025) · unique active community water systems with complete monitoring · January 2026 release
Interpretation
Darker color indicates a higher system-level value for the selected metric. It does not establish household service, exposure, or compliance.
Coverage
UCMR 5 did not comprehensively monitor every small system. Private wells are excluded, and unmonitored systems cannot be assumed negative.
Methods
Read the full methodology for cohort rules, sampling-location averages, comparisons, and limitations.