$1 billion expansion of wastewater treatment plant poised to break ground

With a major expansion on the horizon for Austin’s Walnut Creek Wastewater Treatment Plant, Mayor Kirk Watson is working with city staff to ensure the $1 billion project goes off without a hitch.

The project, which City Council approved last May, would expand the site’s processing capacity from 75 million to 100 million gallons of water per day, while replacing aging equipment, updating treatment processes, and improving flood resilience. If all goes as planned, the project will break ground this summer, with construction continuing through 2031.

For nearly 50 years, the Walnut Creek treatment plant has performed the thankless but vital task of handling roughly half of the city’s wastewater, which undergoes a thorough cleaning and treatment process before returning to the Colorado River, along with a smaller amount that is recycled through the city’s reclaimed water system.

Austin Water managing engineer Lauren King says a lot has changed since 2005, when the Walnut Creek plant underwent its last major renovation. An explosion of population and industry growth has increased demand, while new approaches to water conservation have affected the quality of the plant’s inflow.

“The city of Austin has been doing a fantastic job with water conservation, and we are using less water per person than we were 20 years ago … but the concentration of the wastewater has really increased. Low-flow toilets and washing machines are all great, but that’s more waste and dirt and less water that comes to our facility,” King said.

In addition to expansion, the project will also rehabilitate some of the plant’s oldest facilities, such as Headworks 1, where trash and solid debris are filtered out in step one of the wastewater treatment process.

“This building since 1977 has seen no major rehabilitation work. This is all the original equipment and electrical controls,” King said. “It is still in operation but it is incredibly difficult to maintain, hard to get parts for, and is degrading as it rusts and ages.”

The project will also add more thorough treatment processes at the plant’s aeration basins, where Austin Water plans to introduce nutrient removal measures that target pollutants like phosphorus and nitrogen, key contributors to the algae blooms plaguing the Colorado River. The plant will benefit from new approaches to the disinfection process, with plans to use ultraviolet light in lieu of chemicals like chlorine that are currently in use.

In light of recent updates to the Atlas 14 flood plain maps, the project will also fund the construction of a nine- to 12-foot wall designed to protect the plant in the event of extreme weather events. 

The project will require a number of amendments to land use code to proceed, prompting Council to take a vote yesterday that prompted some criticism from environmentalists. Leading the charge was the Save Our Springs Alliance, which argued that the money would be better spent on water conservation measures and addressing the growing rate of water lost to leaky pipes, while also raising concerns about the cost to ratepayers.

“We’re not in an urgent need to expand this facility under the Texas Commission on Environmental Quality’s 75/90 rule,” Save Our Springs attorney Bobby Levinski said. “Yes, there was a momentary blip into 75 percent capacity that triggered the need to start planning for the expansion, but until the facility hits that 90 percent figure, that’s when you have to start doing construction.”

In fact, Austin Water told the Austin Monitor that the plant hovered above the 90-percent capacity cap for three months in 2024. TCEQ requires plants to begin expansion once 90 percent capacity is met over a three-month period.

Still, Council’s vote to move forward and identify necessary code amendments was nearly unanimous, with the exception of District 10 Council Member Marc Duchen, who opted to abstain. The city manager will return with further details by May 8.

“We sorely need investment in our wastewater infrastructure, both in capacity because of the growth that has happened in Austin, and also capital investment in areas where infrastructure is failing because of age,” District 6 Council Member Krista Laine said. “We also need capital investment in our water infrastructure where it is aging and leaking at ever increasing rates. It is not an either-or: We need to do both.”

In the meantime, readers can check out a more detailed breakdown of project details and costs here.

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Posted In: Water, District 1