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Posted on: March 20, 2019

Public Notice of Total Trihalomethane and Haloacetic Acid MCL Violations

The Texas Commission on Environmental Quality TCEQ) has notified the CITY  OF HORSESHOE  BAY  TX1500015 that the drinking water being supplied to customers had exceeded the Maximum Contaminant Level (MCL) for total trihalomethanes. The U.S. Environment Protection Agency (U.S. EPA) has established the MCL for total trihalomethanes to be 0.080 milligrams per liter (mg/L) based on locational running annual average (LRAA) and has determined that it is a health concern at levels above the MCL. Analysis of drinking water in your community for total trihalomethanes indicates a compliance value in quarter one of 2019 of 0.095 mg/L for DBP2‐01 and 0.085 for DBP2‐02.

Trihalomethanes are a group of volatile organic compounds that are formed when chlorine, added to the water during the treatment process for disinfection, reacts with naturally‐occurring organic matter in the water.  

Some people who drink water containing trihalomethanes in excess of the MCL over many years may experience problems with their liver, kidney, or central nervous systems, and may have an increased risk of getting cancer.  

The  Texas Commission on Environmental  Quality  (TCEQ) has notified the CITY  OF HORSESHOE  BAY  TX1500015 that the drinking water being supplied to customers had exceeded the Maximum Contaminant Level (MCL) for Haloacetic Acids (group of five). The U.S. Environment Protection Agency (U.S. EPA) has established the MCL  for  Haloacetic Acids to be  0.060  milligrams per liter  (mg/L) based on locational running annual average (LRAA) and has determined that it is a health concern at levels above the MCL. Analysis of drinking water in your community for Haloacetic Acids indicates a compliance value in quarter-one of 2019 of 0.062 mg/L for DBP2‐01.  

Haloacetic Acids are a group of volatile organic compounds that are formed when Chlorine, added to the water during the treatment process for disinfection, reacts with naturally occurring organic matter in the water.  

Some people who drink water containing Haloacetic Acids in excess of the MCL over many years have an increased risk of getting cancer.  

You do not need to use an alternative water supply. However, if you have health concerns, you may want to talk to a doctor to get more information about how this may affect you.  
The flood event in October 2018 brought with it large amounts of decaying organic material. The high levels of organic material increased the organic compounds in the lake water that interacted with the Chlorine disinfection used at the water plants consequently producing higher concentrations of both Total Trihalomethanes and Haloacetic Acids in the 1st Quarter of 2019. These constituent samples increased the 4‐quarter running annual averages (LRAA) to exceeded compliance levels for Total Trihalomethanes to 0.095mg/L and Haloacetic Acids to 0.062 mg/L.  Since being notified of the exceedance in late January the City Staff have lowered Chlorine levels.  The concentration of organics in the lake has steadily dropped since January and with the recent filling of the lake, the City’s source water has returned to normal levels.

Since the City was notified of the violation, mitigating this issue has been our highest priority. Continued monitoring and treatment optimization show that the City is still producing safe drinking water based on a recent sample of Total Trihalomethanes of 0.034 mg/L which is well below 0.080 mg/L.  

If you have questions regarding this matter, you may contact Josh Hisey at 830‐598‐9983.

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