401 KAR 8:250.  Inorganic chemical sampling, analytical techniques and maximum contaminant levels.

A system that uses a groundwater source shall collect one sample per entry point to the distribution system (EPTDS) or representative site of each source per year.  A system that uses a surface water source shall collect one sample per quarter per EPTDS or representative site of each source for four consecutive quarters at initiation of water system operation.  Thereafter, the system shall collect one sample per year.  If a sample exceeds 5 mg/L the system shall initiate quarterly monitoring.  A system shall sample for a minimum of four consecutive quarters with results less than the maximum contaminant level (MCL).  Afterwards, with Drinking Water Branch approval, the system shall sample annually during highest "historical" quarter.  If a sample exceeds the MCL the system shall collect a confirmation sample within 24 hours or immediately notify the public.  A confirmation sample collected within two weeks at the same sampling point as an MCL exceedance may be averaged with the first sample to determine compliance.

Technical fact sheet from EPA for nitrate.