The radionuclides rule protects public health by reducing exposure to all radionuclides and covers all size categories of community water systems. 

What to Do If There's an Exceedance

Radiochemical Maximum Contaminant Level (MCL)

If a system exceeds a radionuclide MCL, the system must begin quarterly monitoring in the following quarter for the analyte that exceeded. If the system is enrolled in the Monitoring Assistance Program (MAP), the MAP sampler will not be responsible for this increased monitoring.

If the result is four times the MCL or higher, the system will receive an MCL violation, which requires a Tier 2 Public Notice.  Otherwise, the system will need to calculate their running annual average to determine if there's an MCL violation.