A system that uses a surface water source shall collect one set of samples per entry point to the distribution system (EPTDS) or representative site of each source per year.  A system that uses a groundwater source shall collect one set of samples per EPTDS or representative site of each source per three-year compliance period. If any contaminant(s) exceeds the respective maximum contaminant levels (MCL), the system shall sample the contaminant quarterly. A surface water system shall sample the contaminant for a minimum of four consecutive quarters with results less than the MCL. A groundwater system shall sample the contaminant for a minimum of two consecutive quarters with results less than the MCL. Afterwards, with Drinking Water Branch approval, the system may return to base monitoring requirements. 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.