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Eagle Ford: Drought relief is hidden in plain sight
Thousands of gallons of water cascade down the “steps” of an aerator basin at the San Antonio Water System’s Twin Oaks Aquifer Storage and Recovery site on Hardy Road near Elmendorf.
ELMENDORF -- On a quiet country road off the nearby interstate, millions of gallons of water cascade down a steep stairstep structure. The only witnesses to the powerful waterfall are some cattle and a few employees of the San Antonio Water System (SAWS). For them, it’s nothing unusual.
For visitors to the SAWS Twin Oaks Aquifer Storage and Recovery (ASR) site, however, the facility is a revelation.
On Hardy Road near the Sandy Oaks Olive Orchard, millions of gallons of water are stored to supply SAWS customers across the San Antonio metropolitan area. Water drawn from the Edwards Aquifer is pumped 24 miles from San Antonio to the well field on Hardy Road, where 29 wells are capable of pumping in or withdrawing water. The site can handle 30 million gallons of water per day. The water pumped in stays near the wells, due to the underlying geology of the Carrizo Aquifer, which is sand, unlike the Edwards Aquifer, comprised of caverns of limestone.
The $260 million ASR installation is designed to hold water from the Edwards Aquifer in storage to supply SAWS customers in times of need, such as drought, said Mark Centennial with SAWS.
“It’s environmental,” Centennial said. “It makes good sense to ‘bank’ the water for the summer and drought. Underground, it’s less vulnerable to contaminants and pollutants.”
The site can store more than 15 billion gallons.
The stairstep structure -- aeration basins -- on the site aerates the water as it’s pumped out, headed to clearwater storage units. The complex also includes an administration building and labs, with a computerized control room and security. SAWS owns 3,200 acres here, which it leased back to the local farmers for production after construction was completed.
SAWS is careful to account for the water pumped in and out, voluntarily complying with pumping restrictions imposed by the Evergreen Underground Water Conservation District, which governs the Carrizo Aquifer.
“We work to minimize the impact on our neighbors,” said Robert Macias. “If any wells are affected [by SAWS activity], we mitigate and adjust.”
This has included drilling a new well or a deeper well for the affected neighbor, Macias said.
During a visit to the site earlier this year by members of the Three Oaks Extension Education Association in Wilson County, SAWS presented information about the ASR, as well as a new project, desalination of brackish groundwater.
This new project is located near the Atascosa-Bexar-Wilson county line.
“Desalination is the technology for the future of water in Texas,” Centennial said.
SAWS is working to retrieve brackish groundwater from the Wilcox Aquifer, deep below the Carrizo Aquifer. The Carrizo supplies most of the drinking water in Wilson County.
Read more about the brackish groundwater project in a future issue of the Wilson County News.
The Twin Oaks Aquifer Storage and Recovery site hosts tours. Contact Jerry Kotzur at the SAWS office in Floresville, 830-393-6300, for more information.
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