laboratory flasks with clear liquid

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Water Quality Laboratory

EPA release second set of UCMR5 data (11/17/23): The fifth cycle of the Unregulated Contaminant Monitoring Rule (UCMR) is currently underway, requiring utilities like Thornton to sample for 30 unregulated contaminants (PFAS compounds and Lithium) before 2025. Not all utilities in Colorado have performed their UCMR5 sampling. The EPA uses the data collected from UCMR5 to inform future regulations based on occurrence and severity of contamination nationally. The first two sets of data from UCMR5 have been released and EPA will continue to release data on a quarterly schedule, follow this link to see all nationwide UCMR5 data. Thornton's UCMR5 PFAS results are in line with our standard PFAS sampling results (see our PFAS page), showing that Thornton continues to make progress in reducing PFAS concentrations in our customer's drinking water. Lithium was detected in Thornton's drinking water (average of 30 ppb) which is above the screening level established by the EPA (10 ppb); the screening level is 1000 times lower than concentrations prescribed medically. See CDPHE's fact sheet on lithium at this link

The city of Thornton Water Quality Laboratory is charged with ensuring that the city's drinking water meets all state and federal drinking water regulations. Thornton has a qualified staff of water utility professionals that understand the importance a water supply plays in the overall quality of life for its community. They are dedicated to providing customers with the best quality of water possible. The water quality laboratory provides water sampling, monitoring, and testing using approved procedures and methods following all regulatory requirements.

Laboratory AnalystTreated water is collected and analyzed weekly at the Wes Brown and Thornton Treatment Plants and in the Thornton water distribution system. Raw water sources are also sampled and closely monitored to protect Thornton's drinking water quality. In addition to providing safe drinking water for Thornton's customers, the laboratory prepares and distributes an annual Water Quality Consumer Confidence Report and investigates water complaints.


If you have any questions or concerns about your tap water, please email WaterQuality@ThorntonCO.gov or call the Water Quality Line at 303-255-7770.