Unregulated Contaminant Monitoring Rule (UCMR)

The Importance of UCMR Testing

Every five years, the U.S. Environmental Protection Agency (EPA) implements the Unregulated Contaminant Monitoring Rule (UCMR). The purpose of UCMR is to collect data from utilities like Houston Public Works about contaminants that may be present in drinking water. The EPA uses this data to decide if specific contaminants occur at frequencies and concentrations high enough to be regulated in the future.

Trace amounts of naturally occurring or man-made substances can sometimes find their way into drinking water supplies, and not all are currently regulated by EPA.

The current analytical methods can detect contaminants at trace levels, but the presence of trace levels does not necessarily pose a safety concern. UCMR testing is part of the federal Safe Drinking Water Act.

UCMR5 Testing

Five of the City of Houston's water systems are participating in the EPA’s fifth round of UCMR testing, known as UCMR5, which requires us to monitor for 30 chemical contaminants using analytical methods approved by EPA. It can be a lengthy process to set drinking water regulations, but it is important that EPA completes its thorough, scientific process to fully understand the potential health impacts, maximum contaminant levels, analytical methods, and treatment methods to provide public utilities with proven, consistent standards.

The City of Houston tests for contaminants including 29 per- and polyfluoroalkyl substances (known as PFAS) and lithium. Testing will take place during the 2023 and 2024 calendar year. Updated results will be made available on a quarterly basis as they are available. For more information on PFAS, click here.

The EPA announced a proposed new drinking water regulation for six PFAS compounds. This regulation, when final, would establish Maximum Contaminant Levels (MCLs) of 4 parts per trillion (ppt) for PFOA and PFOS as individual contaminants, and for four others (PFNA, PFHxS, PFBS and HFPO-DA) as a mixture, limited to 1 ppt. The proposed “mixture” MCL of the other four compounds is set at a Hazard Index of 1.0.

This will be determined by a calculation shown in the table below. It's important to keep in mind that no health standards (for example, maximum contaminant levels) have been established at the present time for any of these unregulated contaminants. The levels listed on these proposed standards are not final and may ultimately change.

PFAS Compound Table

If you would like more information on the EPA’s Unregulated Contaminants Monitoring Rule (UCMR),
please call the federal Safe Drinking Water Hotline at (800) 426-4791.
For more information about Houston's test results, call 832-395-3113 or email [email protected].


UCMR 5 Sampling Results (Entry Point to Distribution)

Click here to see detailed results for the Main System PWS1010013 - Samples scheduled for February, May, August, and November 2023
Click here to see detailed results for the Kingwood System PWS1010348 - Samples scheduled for June and December 2023
Click here to see detailed results for the Willow Chase System PWS1011902 - Samples scheduled for January and July 2024
Click here to see detailed results for the District 73 System PWS1011585 - Samples scheduled for June and December 2024
Click here to see detailed results for the District 82 System PWS1011593 - Samples schedule for February and August 2024

For additional information on UCMR 5 go to: https://www.epa.gov/dwucmr

Timeline for EPA Drinking Water Regulations for PFAS

Contact Information

or email:
[email protected]