CITY OF SAN MARCOS
The City of San Marcos received a notice of violation from the Texas Commission on Environmental Quality (TCEQ) after one of eight water sampling locations, 345 Champions Blvd, recorded slightly elevated levels of Total Trihalomethanes (TTHMs) of 0.081 milligrams per liter (mg/L) which is above the Maximum Contaminant Level (MCL) of 0.080 mg/L based on a locational running annual average (LRAA).
TTHMs are by-products that can form when chlorine, used to disinfect drinking water, reacts with naturally occurring organic materials. Chlorine is required by both TCEQ and the En- vironmental Protection Agency (EPA) to ensure harmful bacteria and viruses are eliminated from the water supply.
Short-term exposure to TTHMs above the MCL does not pose an immediate health risk. According to TCEQ, people who drink water containing TTHMs in excess of the MCL over many years may experience problems with their liver, kidneys, or central nervous system and may have an increased risk of certain cancers.
The City has taken corrective actions, including flushing targeted areas of the system to improve water circulation, adjusting what source waters we’re using, and increasing sampling frequency to closely monitor improvements in water quality.
“Our corrective actions have showed positive results,” said SMTX Utilities Assistant Director Paul Kite. “As of the most recent water distribution system sampling conducted on November 19, 2025, at 345 Champions Blvd, showed TTHMs levels of 0.016 mg/L, which is below the regulatory limit.”
The City will continue to coordinate with GBRA and TCEQ to monitor source water quality at Lake Dunlap, adjust treatment processes as conditions change, and strive to maintain full compliance with all state and federal drinking water standards.
SMTX Utilities water customers have been notified through direct mail, and updates will be shared as additional test results become available at sanmarcostx. gov/tthms.
