Wastewater runoff drives algal blooms in San Gabriel

The presence of algae has been traced back to high phosphorus levels found in the effluent, or treated wastewater, discharged from Liberty Hill’s wastewater plant. After years of ongoing litigation, the TCEQ is now requiring Liberty Hill to look at improving the plant.

The background

The South Fork Wastewater Treatment Plant’s recent issues date back to 2018 when the TCEQ found several violations with the facility.

“As the [city] grows, it remains committed to environmentally responsible, scientifically sound solutions for wastewater management that meet TCEQ standards,” a statement from the city reads.

After pending for six years, the TCEQ issued the South Fork WWTP’s permit renewal in April, which allows it to increase its effluent from 2 million to 4 million gallons per day.

The South Fork WWTP’s discharge was exceeding TCEQ’s limits for dissolved solids, chloride and sulfate, David Thomison, Liberty Hill director of public works, said at a Sept. 11 City Council meeting. Thomison said the plant wasn’t designed to meet the low levels set by the TCEQ.

The average phosphorus levels in Liberty Hill’s effluent from December 2022-

April 2023 was between 0.05-0.08 milligrams per liter, per TCEQ documents.

Per TCEQ, Liberty Hill is required to conduct a total dissolved solids, chloride and sulfate source work plan study, which costs $185,287. The TCEQ approved the plan, in which the city partners with Garver Engineering, a firm that will prepare annual progress reports in December. Liberty Hill still needs to submit a separate phosphorus work plan study.

Charting the Waters

• May 2018: TCEQ begins and investigation into the South Fork WWTP
• Sept. 2018: TCEQ receives Liberty Hill's request to renew its wastewater permit and increase effluent limits
• June 2020: Pending corrective action, Liberty Hill is fined about $100,000 for eight violations
• April 2024: The TCEQ approves the 2018 permit renewal request and orders the city to reduce phosphorous levels from 0.15 milligrams per liter to 0.02 mg/L
• May 2024: Liberty Hill submits a motion for rehearing, calls effluent limit "technically impossible"

Phosphorus is an essential element needed for all life and is usually prominent in fertilizers, said Weston Nowlin, a biology professor at Texas State University. Phosphorus alone isn’t necessarily harmful, he said.

However, water with high levels of phosphorus and nitrogen usually leads to algae and bacterial growth, along with lower water quality. Someone swimming in that water runs a higher risk of getting sick, Nowlin said.

The growth and decay of algae also produces odors, Nowlin said. While he can’t identify the specific kind of algae in the South Fork San Gabriel River—nuisance, mutant or harmful—Nowlin said algal mats he’s seen from photos are “not good.”

When Georgetown’s Garey Park first opened on the other side of Bunnell’s property, he said he became concerned about the health of people in the water.

“There were kids coming down, playing in the river, so I got very concerned that someone was going to get very sick,” Bunnell said.

Wastewater treatment process

1. Water from residential and business drains collects in the sewer, where it’s transported to a nearby lift station and then to the wastewater treatment plant.
2. Inorganic material in the wastewater is removed and hauled away, while the rest is treated, filtered and disinfected.
3. Some of the treated effluent is recycled and used for cleaning the plant, but the remainder is discharged into waterways. The South Fork WWTP discharges into the San Gabriel River.

Within the city’s 2018 permit renewal application for the South Fork WWTP was a request to double the facility’s effluent discharge. The TCEQ approved this increase in April, with the caveat that the city must complete a 36-month study into improving the plant and lower the phosphorus levels further.

“You’re causing even more—probably—water quality problems if you’re increasing the total volume of your discharge but keeping the effluent concentration the same,” Nowlin said.

The city plans to build two more wastewater plants in north and west Liberty Hill, and the South Fork WWTP has experienced expansion delays.

Residents inquired about Liberty Hill’s proposed north WWTP in the Saddleback community at a Dec. 3 TCEQ public meeting. Construction details are pending, said Vince Perkins, Liberty Hill safety and compliance environmental coordinator.

The effluent would discharge into the North Fork San Gabriel River, which flows into Lake Georgetown—a public drinking water source.

According to the draft permit, the plant’s final phase phosphorus effluent limitations will be 25 times greater than the South Fork WWTP’s. A TCEQ official said these limits were designed specifically for the uses of the North Fork San Gabriel River.

Liberty Hill is not the only Central Texas city dealing with wastewater capacity issues as its population grows.

In 2019, the TCEQ granted the city of Dripping Springs a permit to expand its wastewater services, but the permit was challenged in court by the Save Our Springs Alliance. As that case progressed, the city entered a development moratorium—or a halt on new construction—from Nov. 18, 2021, to Sept. 18, 2022. While the moratorium has ended, the city is still searching for solutions as the case is pending before the Texas Supreme Court.

In May, the city of Bastrop announced its new $32.6 million wastewater treatment plant was online. However, further expansion plans, which were held up in court for years, have now been greenlighted. Due to the plans’ lengthy postponement, the city is going back to the drawing board to increase their scope.

And on the outskirts of Hutto and Pflugerville city limits, developers are building packaging plants—small-scale wastewater treatment facilities that serve a development or neighborhood—leading to concerns from some residents and officials about the environmental impact of such options.

While some Central Texas areas are seeing a slowdown in growth, Liberty Hill is expecting higher water demands in the next 20 years.

Liberty Hill’s approved work plan with Garver includes coordinating with the city and TCEQ to discuss alternative solutions for meeting phosphorus limits. Liberty Hill has yet to submit a separate work plan for a phosphorus study, a TCEQ official said.

“The [city] assures the community that all decisions will continue to be based on strong science, data and legal compliance to protect the health, safety and well-being of Liberty Hill and Central Texas,” a city statement regarding the South Fork WWTP reads.

The city of Liberty Hill declined Community Impact’s request for interviews due to ongoing litigation.

“The conflict that we’re seeing here between management of water resources in the rivers, and then dealing with an increasing population in Central Texas ... is going to get increasingly more common,” Nowlin said.