Updated December 2024

Every five years, the Environmental Protection Agency (EPA) reviews and selects a list of unregulated contaminants for public water systems to monitor. This study benefits the environment and public health by providing valid data on the occurrence of these contaminants in drinking water. The EPA uses this data to develop regulatory decisions for emerging contaminants. This requirement is mandatory for all public water systems that serve more than 10,000 customers.

UCMR5 requires testing for 29 per- and polyfluoroalkyl substances (PFAS) and lithium. This list includes the PFAS chemicals that EPA is proposing new Maximum Contaminant Levels (MCLs): PFOA and PFOS as individual contaminants, as well as PFHxS, PFNA, PFBS and HFPO-DA (commonly referred to as GenX Chemicals) as a PFAS mixture.  

In 2024, Prince William Water collected quarterly samples for the Unregulated Contaminant Monitoring Rule 5 (UCMR5) in its East and West water distribution systems. Results indicated that Prince William Water's East system were slightly above the EPA's proposed Maximum Contaminant Level for both PFOA and PFOS. PFOA and PFOS were not present in the sampling performed for Prince William Water's west system.

Prince William Water will work with regulatory agencies and our wholesale water providers to ensure that we maintain the safety and high quality of our drinking water. Water systems have until 2029 to comply with the EPA’s stringent new PFAS limits.