4/20/2026 Seasonal Update: The Wes Brown Water Treatment Plant will be brought into service in the coming days following a winter maintenance period. The plant will be predominantly treating the South Platte River source. Though we strive to make these changes as seamless as possible, customers may notice some aesthetic changes including increased mineral content and hardness, or differences in taste.
Please refer to our FAQs further down this page for tips on addressing these issues at home.
The Environmental Protection Agency (EPA) releases UCMR5 data: The Unregulated Contaminant Monitoring Rule (UCMR) requires utilities like Thornton to sample for 30 unregulated contaminants (PFAS compounds and lithium). The EPA uses the data collected from UCMR5 to inform future regulations based on the occurrence and severity of contamination nationally. All data has been collected and released; visit the EPA's UCMR5 Data Finder page to see all available data nationwide. Thornton's UCMR5 PFAS results align with our standard PFAS sampling results (visit Thornton's PFAS Information page), showing that Thornton continues to progress in reducing PFAS concentrations in our customer's drinking water. Lithium was detected in Thornton's drinking water (average of 30 ppb), above the screening level established by the EPA (10 ppb); the screening level is 1000 times lower than concentrations prescribed medically. For further information on lithium in drinking water visit the Colorado Department of Public Health and Environment's factsheet.
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 who understand the importance of a water supply in its community's overall quality of life. 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.
Treated 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. The current Water Quality Report is linked at the top of this page; previous years' reports are available by request at the contact points listed on the left side of this page.
