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Research Helps Ensure High-Quality Louisville Pure Tap®

Louisville Water’s core mission is based on public health and safety. Every day, nearly one million people depend on us for high-quality and reliable drinking water.

The Environmental Protection Agency (EPA) regulates public water providers using regulations developed under the Safe Drinking Water Act. Research on the occurrence and potential public health effects of various chemicals helps EPA decide which chemicals to regulate and at what levels to ensure high-quality, safe drinking water. Louisville Water conducts required monitoring and independent research and works with other utilities and national organizations to advance the science of drinking water treatment, improve our processes, and prepare for new, more stringent regulations.

Louisville Water is one of more than 10,000 public water systems participating in research for 30 chemicals that are not currently regulated. Called the “Fifth Unregulated Contaminant Monitoring Rule,” or UCMR 5, this EPA mandate requires utilities to sample for the presence of 29 PFAS chemicals and one metal, lithium, in drinking water. UCMR 5 provides data that helps EPA and utilities understand the occurrence of the chemicals in drinking water, including the concentration and frequency. This data is part of science-based decisions for possible future regulation.

Under UCMR 5, utilities are required to monitor for the target chemicals and report their findings to the EPA during a 12-month period between January 2023 and December 2025. EPA then publishes the monitoring results quarterly.

Louisville Water has completed its UCMR 5 monitoring. Samples are analyzed by our contract laboratory and reported to EPA before they are reviewed and published.

UCMR5 monitoring is for 30 chemicals not currently regulated and Louisville Water detected four of the chemicals. This table highlights the chemicals we detected, the running annual average and the ranges for detected compounds. The running annual averages you see are calculated based on quarterly monitoring. The acronym “BDL” means below detection limit and the chemicals are measured in parts per trillion (ppt).

Unregulated Substances - Treatment Plants
Water Quality Data (Jan 1 - Dec 31, 2023)
Crescent Hill Filter Plant (CHFP)
B.E. Payne Water Treatment Plant (BEP)
Substance (units)
Minimum Reporting Level
CHFP average
Range of Detections
BEP average
Range of Detections
Perfluorooctanoic Acid (PFOA) (ppt)
BDL - 7.5
Perfluorobutanesulfonic Acid (PFBS) (ppt)
BDL - 3.0
Perfluorohexanoic Acid (PFHxA) (ppt)
BDL - 3.6
Perfluoropentanoic Acid (PFPeA) (ppt)
BDL - 4.1


The UCMR 5 target chemicals included a group of six PFAS chemicals that EPA will regulate. PFOA is the only one of the six chemicals Louisville Water detected, and the running annual average is below EPA’s regulation.

We continue to research how to further reduce the presence of PFAS chemicals in our drinking water through advanced treatment options. PFAS are manufactured chemicals that do not naturally occur. Louisville Water also supports efforts to minimize the risk of these chemicals getting into the environment.

Beyond UCMR 5, Louisville Water conducts hundreds of tests daily to ensure safe drinking water and each year we share the Annual Water Quality Report with our community. Louisville Water meets all state and federal regulations for water quality; the report also details the testing we do and explains the water treatment process.