Some Big Spring residents are receiving water quality notices in the mail after routine testing found elevated levels of a regulated disinfectant byproduct in the city's drinking water system, according to the City of Big Spring and the Texas Commission on Environmental Quality.

The notices follow findings that total trihalomethanes, or TTHMs, exceeded federal safety standards in parts of the system throughout 2025.

According to the U.S. Environmental Protection Agency, the maximum allowable level for TTHMs in drinking water is 0. 080 milligrams per liter, or 80 parts per billion.