Total Trihalomethanes (TTHM) and Haloacetic Acids (HAA5) are disinfection byproducts that are monitored quarterly by the Texas Commission on Environmental Quality (TCEQ). The results in this data set are calculated quarterly averages by site using the results from each sample location. Sample data for each location is available on the TTHM and HAA5 pages.

TCEQ uses contract samplers to collect all TTHM and HAA5 samples use for compliance with the Stage 2 Disinfection Byproduct Rule. The results in this data set are from all TTHM & HAA samples collected since January 1, 2017.