City of San Marcos Notifies Water Customers of System Violation

The City of San Marcos is sending out notification letters to all water customers informing them of levels of a contaminant in the water system that exceeded state regulations during the first quarter of 2016. The water system currently meets state regulations, and at no time was the City’s drinking water unsafe to consume. 

On April 12, 2016, a notice of violation letter was received from the Texas Commission on Environmental Quality (TCEQ) confirming that the City’s water system had exceeded a Total Trihalomethanes (TTHM) Maximum Contaminant Level (MCL) with a count of 0.082 mg/L for the first quarter of 2016 for the sampling location at 2700 Centerpoint Road. A violation occurs if the average for four consecutive quarters exceeds the MCL of 0.080 mg/L.

This violation requires a public notice be sent to all customers of the water system. Notices will be mailed directly to the customer in conjunction with posting the notice in public places (City Hall, Library, etc.).

The sample taken during the first quarter of 2016 was 0.079 mg/l, lower than the maximum contaminate level, but not low enough to bring the average below the MCL due to the third and fourth quarter results of 2015, which were 0.0915 mg/L and 0.0874 mg/L respectively.

The area in the vicinity of 2700 Centerpoint was the area affected; however, the TCEQ requires that all water customers of the City be sent a notice informing them of the violation. An additional sample taken at 2700 Centerpoint by City staff on Wednesday, March 30, 2016 showed a TTHM result of 0.046 mg/L, well within state regulations.

Actions being taken by the City

An automatic flush valve is being installed near 2700 Centerpoint to increase water flow into this area and help reduce the formation of these compounds.

City staff members are also working with Guadalupe-Blanco River Authority (GBRA) and Alan Plummer Associates, Inc. (APAI) on a project to develop and investigate solutions for reducing the formation of TTHM, and other disinfection by-products, at the Surface Water Treatment Plant and throughout the distribution system.  APAI will have the final report submitted to the City by mid-May 2016.  Funding for improvements recommended by the study will be requested in the Fiscal Year 2017 Water and Wastewater Budget.

What are TTHMS?

TTHMs are formed when chlorine, used to disinfect the drinking water, reacts with naturally occurring organic matter in the water. The longer the water is in the pipe, the more these compounds are formed.  The sampling location at 2700 Centerpoint is one of the farthest from the Surface Water Treatment Plant, and thus water in that location spends the longest time in the pipes before being used or flushed.

According to TCEQ, 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. City staff and state regulators work together to ensure water never contains these compounds above the MCL for such extended periods.

For more information, contact Jon Clack, Assistant Director of Public Service-Water/Waste Water Division, at512.393.8010.