Water Quality

The Environmental Protection Agency (EPA) released a 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 the occurrence and severity of contamination nationally. The first two sets of data from UCMR5 have been released, and the EPA will continue to release them quarterly. 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 page link above), 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 of 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.

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.

An analyst in a white lab coat stands to the right of an advanced laboratory instrument.

Water Quality Frequently Asked Questions