Zachry completes largest desal plant in U.S.

February 2, 2017

Zachry Construction completed the largest inland desalination plants in the United States. 

San Antonio's newest source of drinking water borrowed drilling techniques from the oil and gas industry to build one of the largest inland desalination plants in the United States. 

The San Antonio Water System held a grand opening on Jan. 27 for the H2Oaks Center off Hard Road just outside Elmendorf.

Drawing from three underground sources, the state-of-the-art desalination plant was designed to take brackish water, filter it and send the waste deep underground.

San Antonio-based general contractor Zachry Construction oversaw the $197 million project, which began in July 2014 and finished earlier this month.

Zachry — which has built highways, parks and some of San Antonio's most iconic buildings — borrowed techniques from its sister company Zachry Exploration to make the H2Oak Center a reality.

The company's crews drilled four wells on the 3,200-acre property and laid 12 miles of pipeline.

One well pumps brackish water up from the Wilcox Sand geological formation 1,600 feet below the surface, while another pumps brackish water up from the Carrizo Sand geological formation about 300 feet below the surface.

A third well takes excess water from the Edwards Aquifer and injects it into the Carrizo Sand formation, where it is stored until it is needed and pumped back up.

Zachry Construction Project Manager Brian Lennard told the Business Journal that the fourth well borrowed drilling techniques and 3-D modeling from its sister company to create an injection well.

Once the plant's reserve osmosis filters remove salts and other impurities from the brackish water, the waste is injected into the porous limestone of the Georgetown, Edwards and Upper Glen Rose geological formations.

Similar to saltwater disposal wells for the oil and gas industry, the H2Oaks injection well uses a concrete casing to protect its steel pipe as it passes through environmentally sensitive geological layers that contain fresh water and brackish water.

With two more phases expected to add another 12 million gallons of capacity, Lennard said Zachry plans to bid on the future projects based on their experience building the H2Oaks Center.

"It's a new market for Zachry," Lennard said. "It was a learning experience for many of us, but we had some experienced people that led the way for us."

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