Any time a MCL is exceeded, what must the NTNCWS do?

When a Maximum Contaminant Level (MCL) is exceeded in a Non-Transient Non-Community Water System (NTNCWS), the required action involves giving notice by continuous posting. This means that the water system must inform its users about the exceedance in a clear and visible way that remains accessible over time. Continuous posting ensures ongoing awareness among consumers regarding the potential risks associated with the water quality issue.

This practice is crucial for public health protection, as it allows consumers to be informed about the contamination, its implications, and any recommended actions they should take, such as using alternative water supplies or treating the water. Effective communication through consistent messaging is a key element in managing public health risks associated with water quality.

The other choices do not align with the regulatory requirements or best practices for communicating about MCL exceedances. While notification via email or conducting a public meeting may be part of broader communication efforts, they do not replace the urgent need for ongoing, visible notice in the community. Decreasing the contaminant level, while a goal for water systems, does not address the immediate requirement for informing consumers about a current exceedance.