City: Water supply contaminant situation isolated, already remedied

BOERNE — The city of Boerne received notification that its drinking water supply contained an elevated level of total trihalomethanes, a situation it has since remedied. 

The Texas Commission on Environmental Quality (TCEQ) informed Boerne that its total trihalomethanes levels during the third quarter of 2024 registered at 0.083 milligrams per liter, exceeding the standard of 0.080 — the equivalent of being over by 3 parts per billion. 

For comparison, 3 parts per billion is equal to about three drops of water in an Olympic-sized pool. 

The alert, the city’s first in 25 years, was confined to a single testing site in the 100 block of Market Street, in the industrial park area. 

“This event occurred due to Boerne Utilities dramatically reducing our groundwater (pumping from wells) production earlier this summer, in response to drought conditions,” said Chris Shadrock, city communications director.  

Boerne Utilities chose to minimize its normal withdrawal, which resulted in a greater mix of surface water in the system, leading to the one elevated rating. 

“We have since corrected the balance of water production and do not anticipate elevated trihalomethanes levels to occur again,” Shadrock said. 

Triahalomethanes are a group of volatile organic compounds that form when chlorine — added to the water supply during the treatment process for disinfection — reacts with naturally occurring organic matter in the water. 

Boerne residents recently received mailed flyers describing the situation and the city’s response efforts. 

Water customers do not need an alternative water supply, as the issue has already been handled. 

Exposure to trihalomethanes in excess of containment levels over a duration of many years could lead to liver, kidney or nervous system issues. 

Boerne Utilities reports the balance as restored and expects future readings to be within acceptable health levels. 

To prevent future occurrences, the city is set to restore the normal mix ratio of groundwater and treated surface water, to bring its system back into compliance. 

Boerne Utilities also is installing a new storage tank mixer and will soon add filters at a pump station, to remove disinfection byproducts and periodic taste-odor compounds often present in treated surface water.