Austin City Council signed off on spending up to $90 million to strip hazardous gaseous chlorine and anhydrous ammonia out of the city's Ullrich Water Treatment Plant, swapping them for disinfection technology officials describe as inherently safer. The vote happened Thursday in west Austin, where the decades-old plant has long relied on chemicals that require specific bulk delivery, storage and handling.
The council authorized a construction-services contract with MGC Contractors to carry out the conversion, according to KXAN Austin. The deal carries a base amount of $81,555,085, plus an $8,155,509 contingency, for a maximum total of $89,710,594, and contractors have 840 days to finish the work.
Once complete, the plant will no longer need gaseous chlorine or anhydrous ammonia for disinfection, per the council document cited in the outlet's report. Instead, Ullrich will generate its own sodium hypochlorite, essentially bleach, on site through electrolysis, a process that converts ordinary salt and water into a 0.8% sodium hypochlorite solution. Anhydrous ammonia will be replaced with liquid ammonium sulfate, which will be stored in liquid, non-hazardous form rather than as a pressurized gas.
How the Switch Will Happen Without Shutting the Plant Down
A temporary sodium hypochlorite storage and feed system will keep disinfection running while crews demolish and replace the existing gaseous chlorine infrastructure, the station's report notes. The plant itself is expected to stay open throughout the transition, with project coordinators working to minimize any impacts to customer service.
Ullrich Water Treatment Plant was commissioned in 1969 and, according to the council document referenced in the same report, supplies a large portion of Austin's potable water. Austin Water's own facilities page separately lists the plant's current capacity at 167 million gallons per day, situating it near Lake Austin and Tom Miller Dam.
A Long-Running Effort to Modernize Disinfection
This is not the first time the city has floated converting Ullrich away from bulk chlorine and ammonia. A city capital projects list once described an onsite sodium-hypochlorite and liquid-ammonium-sulfate conversion at the plant, with an estimated construction period of winter 2022 through 2025, and a preliminary engineering report had evaluated options including that same onsite generation approach, according to city documents. A separate city record from April noted that several Austin Water capital efforts, including work tied to Ullrich, had progressed beyond original assumptions because of changed field conditions and contractor delivery constraints.
Austin is not alone in moving away from gaseous disinfection chemicals. In Columbus, Ohio, the city's largest water plant was reported in 2023 to be switching from chlorine gas to a safer system, following an earlier conversion of its Dublin Road Water Plant to sodium hypochlorite back in 2008, according to 10TV. The Tarrant Regional Water District in Texas has outlined similar plans to replace a chlorine system with sodium hypochlorite, a move it said would reduce hazards and eliminate certain federal regulatory requirements, per the Tarrant Regional Water District.
For now, Austin Water's contract with MGC Contractors gives the agency up to 840 days to complete the Ullrich conversion, with funding already available in the utility's capital budget to cover the full $89,710,594 maximum. The move brings one of the city's oldest and largest treatment plants in line with a broader industry shift toward safer, on-site chemical generation over bulk hazardous deliveries.
