Understanding the Recent TTHM Water Quality Notice

We understand residents may have questions about the recent water quality report distributed to Runaway Bay water customers.

At the April 15, 2026 City Council meeting, Public Works Director Ryan Halligan and Public Works Consultant Roddy Boston provided a detailed update regarding the City’s water system, treatment process, and ongoing efforts to address Total Trihalomethanes (TTHMs). With the release of the latest report, we’d like to revisit that information and provide additional context for residents.

The recent notice was required by the Texas Commission on Environmental Quality (TCEQ) because one monitoring location slightly exceeded the federal standard for Total Trihalomethanes (TTHMs) based on a Locational Running Annual Average (LRAA). This average is calculated using multiple quarters of testing data rather than a single water sample.

TTHMs are regulated compounds that can form when chlorine, which is used to disinfect drinking water, reacts with naturally occurring organic material in the water. As discussed during the April Council meeting, this is a common and closely monitored issue for water systems across Texas and the United States.

While the annual average remains slightly above the allowable limit at one monitoring location, recent testing shows a significant downward trend and demonstrates that corrective actions are working.

Since late 2025, the City has adjusted treatment practices, including changes to chemical dosing and timing, to reduce TTHM levels throughout the system. Those efforts have produced measurable improvements. Recent quarterly results at the affected location have steadily declined, with the most recent reading measuring 0.069 mg/L—below the federal limit of 0.080 mg/L. In addition, the City’s other monitoring locations are currently in compliance.

It is important to understand that the notice is based on a running annual average rather than a single test result. Because the calculation includes older readings from previous quarters, the compliance average remains slightly above the regulatory threshold even though recent testing results have improved significantly.

Ryan emphasized that this notice does not indicate an immediate health risk. Residents do not need to use an alternative water source, and the notice was issued as part of the regulatory process required by TCEQ when a monitoring location exceeds the established standard.

The City will continue working closely with TCEQ, monitoring water quality, and making operational adjustments as needed to ensure full compliance is maintained throughout the system.

The slides below were presented during the April 15, 2026 City Council meeting and provide additional information regarding TTHM monitoring, treatment adjustments, and recent water quality trends.