What happens if the MCL Exceeded?
A public water supply exceeds the MCL if a nitrate result is above 10mg/L. A confirmation sample for nitrates must be collected within 24 hours of receiving notification of the results from the lab. When a MCL violation is confirmed, public notice must be provided to consumers within 24 hours of being notified by the Department of Environmental Quality (DEQ). The system then has ten days to provide proof that the public notice was issued back to DEQ. Systems that are sampling once a year will receive notification of increased monitoring for nitrates from DEQ. The system will monitor quarterly (once every three months) for at least four quarter. This increased monitoring may be required until a system is reliably and consistently below the MCL. Systems must remain on increased monitoring until notified in writing by DEQ that they can resume annual monitoring.
