Existing plants may have more useful life and capacity left in them than their age suggests
Texas communities need more wastewater capacity, but meeting the need does not necessarily mean abandoning an existing plant. Many older facilities still have valuable infrastructure in place. Upgrading them can extend service life, improve performance, and clear the way for future growth while preserving assets that still have years of use left.
Austin Water’s Walnut Creek Wastewater Treatment Plant serves as a good example. The facility is nearing a half-century of service and treats more than half of the city’s wastewater.
Rather than replace a system on Walnut Creek’s scale, Austin is expanding and modernizing the existing facility. The $1.5 billion project will increase the plant’s permitted capacity from 75 MGD to 100 MGD.
Deciding the extent of rehabilitation a facility needs begins with determining which assets still hold long-term value and where replacement, retrofitting, consolidation, or expansion makes the most sense.
Why Existing Plants Are Getting a Second Look
Existing wastewater plants can hold a great deal of value, some of which exists outside the plant itself. Some assets and underlying civil infrastructure that would be lost and could be expensive to duplicate with a full replacement might include:
- Established treatment basins
- Sound buildings
- Costly conveyance connections
- Discharge infrastructure
- Electrical service
With a functional plant, a component-level evaluation lets utilities determine what needs to be addressed and the best way to address it. Engineers can assess basins, influent channels, clarification equipment, disinfection systems, solids handling, controls, and other treatment stages individually rather than treating rehabilitation and full replacement as the only two choices.
If the existing site can support modern equipment, additional capacity, or a more efficient treatment configuration, rehabilitation or expansion may become a more practical option. Utilities can direct capital toward the improvements that will enhance performance without major disruption.
Capacity, Condition, and Compliance Shape the Plan
The right approach depends on current flows, expected demand, equipment condition, regulatory requirements, available land, available capital, solids handling and disposal needs, and the construction schedule. Utilities also need to consider whether the plant can keep operating during improvements or whether it will need temporary bypass capacity.
Walnut Creek illustrates how several factors can converge. Plant flows exceeded 75% of capacity in 2015 and surpassed 90% for three months in 2024, triggering state expansion requirements. The project will:
- Replace aging components
- Add advanced nutrient removal
- Convert chlorine disinfection to ultraviolet disinfection
- Rehabilitate headworks
- Improve odor control
- Expand peak flow capacity
- Provide flood protection
Phased Expansion Aligns Investment With Growth
Not every facility needs to add its full projected capacity at one time. Phased expansion lets a utility add capacity as demand materializes, preserving capital for other infrastructure until the next phase moves forward.
AUC used this type of expansion approach with the City of Magnolia, Texas, where the existing wastewater treatment plant needed more capacity to support continued growth. AUC added a 750,000 GPD steel concentric unit and tied it into the plant’s existing hydraulics and process flow, increasing total facility capacity to approximately 1.3 MGD.
The expansion gave Magnolia additional capacity for current needs while leaving room for future expansion. For utilities with usable infrastructure already in place, expansion can add needed capacity without requiring them to start over.
Underperforming Facilities May Still Hold Long-Term Value
Deferred maintenance, aging equipment, and rising demand can weaken performance without negating a facility’s underlying value. Basins, buildings, connections, land, and other infrastructure may still be worth retaining even when a plant needs significant investment.
For an underperforming or underfunded facility, acquisition may offer another path. A utility may have infrastructure worth preserving but lack the capital or resources to make the improvements it needs. New ownership and investment can create an opportunity to rehabilitate aging components, improve performance, add capacity where needed, and continue using the assets already in place.
Getting More From Existing Infrastructure
Selective replacement can offer a better path than either preserving an inefficient legacy system or completely replacing it. Where an expansion requires additional clarification capacity, for instance, consolidating smaller clarifiers into a single large clarifier can add capacity and recover land while reducing the number of mechanical assemblies.
A rehabilitation plan may combine retained structures, repaired assets, new treatment technology, and phased capacity. For municipalities facing capital constraints, options such as leased infrastructure can also reduce the immediate capital burden.
AUC Group is currently evaluating opportunities involving underperforming or underfunded wastewater facilities in Texas, including facilities where new investment, rehabilitation, or additional capacity could extend the value of existing infrastructure. Contact AUC to discuss an existing facility.
