401 KAR 8:510. Disinfectant residuals, disinfection byproducts and disinfection byproduct precursors.
A system that produces water shall monitor throughout the distribution system. A system that produces and provides water to another system shall be responsible for monitoring throughout the joint distribution system. Samples shall be collected according to the approved sample site plan.
For surface water and groundwater under the direct influence of surface water systems that serve a population greater than 10,000 people, collect three distribution samples and one sample reflecting maximum residence time per plant per quarter. Systems serving a population of 500-9,999 people, collect one sample per plant per quarter reflecting maximum residence time. Systems that serve a population fewer than 500 people, collect one sample per plant per year reflecting maximum residence time during the warmest month.
For groundwater systems serving a population of more than 10,000 people, collect one sample per plant per quarter reflecting maximum residence time. Groundwater systems that serve a population fewer than 10,000 people, collect one sample per plant per year reflecting maximum residence time during the warmest month.
Compliance is determined on a four-quarter running annual average with a maximum contaminant level (MCL) of 0.080 mg/L for total trihalomethanes (TTHMs) and 0.060 mg/L for haloacetic acids (HAA5s). Systems sampling less than quarterly that exceed a MCL shall complete four consecutive quarters before compliance can be determined.
With approval from the Drinking Water Branch, systems may reduce monitoring if
- the annual source water total organic carbon is less than or equal to 4.0 mg/L,
- the annual average for TTHMs is less than or equal to 0.040 mg/L and
- the annual average for HAA5s is less than or equal to 0.030 mg/L.
Refer to the table in 401 KAR 8:510 for reduced monitoring frequency for TTHM and HAA5.
