Austin Water seeks variances and code amendments to expand Walnut Creek wastewater plant to 100 million gallons per day

Austin Water presented plans and a request for administrative variances to facilitate the expansion and enhancement of the Walnut Creek Wastewater Treatment Plant during a committee briefing. The utility said it plans to add 25 million gallons per day to increase the plant’s rated capacity from 75 million to 100 million gallons per day, convert the existing treatment process to biological nutrient removal, install ultraviolet disinfection, and construct a flood wall to protect the site from updated flood-plain modeling.

The project team described the expansion as a generational capital program, noting that the City Council previously approved design and construction contracts of roughly $1 billion for work at Walnut Creek. Austin Water said construction will be delivered in multiple packages using a construction-manager-at-risk (CMAR) model to allow earlier procurement of long-lead equipment and to coordinate complex sequencing needed to maintain continuous plant operations during construction.

Why it matters: Austin Water reported that plant flows exceeded 90% of treatment capacity for three months in 2024 (January, February and May), a level that the utility said triggers a Texas Commission on Environmental Quality (TCEQ) requirement to begin construction. City staff warned that…