Inside H2Oaks, San Antonio’s 3-In-1 Water Plant

Behind the glass pane, three men sat behind a panel of computer screens at what looked like a miniature version of NASA’s mission control center.

Instead of launching spacecraft, the men were concerned with what was going on below ground. Sitting at their computers, they manipulated the flow of water into and out of three underground rock layers and the larger network of pipes that connect to 1.7 million people in the San Antonio area.

It was just another day at the San Antonio Water System’s H2Oaks plant.

Outside the glass on Thursday stood a group of water utility professionals from around the state. They had signed up to tour the plant as part of the Texas Water 2018 conference, put on by the Water Environment Association of Texas and the Texas Section of the American Water Works Association.

“I love this thing – I am a geek for this,” said Eduardo Parra, a civil engineer recently appointed to SAWS’ board of trustees, seeing the completed plant for the first time.

At the outset, Jeff Haby, a SAWS vice president, explained how the whole system is designed to take advantage of three aquifers stacked like a layer cake below the plant.

There’s the Edwards Aquifer, a vast limestone water rock layer that stores freshwater below most of San Antonio but turns salty by South Bexar County. There’s also the Carrizo Aquifer, used to produce and store fresh water, and the Wilcox Aquifer, which at that location is slightly salty.

Wells and pumps at H2Oaks pump fresh water from the Carrizo, which is then treated to chemically match water from the Edwards – San Antonio’s main water source.

“You have to condition your water to what your pipes are used to seeing,” said Richard Donat, a SAWS senior resource analyst who led the tour.

“Otherwise, you have a Flint, Michigan, situation,” he said, referring to how that city’s water utility switched to a supply that leached lead from the city’s pipes.

At H2Oaks, operators can take water pumped from the Edwards and piped south and store it in an underground water bank known as the ASR, for aquifer storage and recovery.

The ASR is basically a giant bubble of water pumped into a layer of sand underground via wells during times of abundant rainfall, then slurped back up to the surface when droughts return.

As of 2017, SAWS had stored more than 143,000 acre-feet of water in the ASR, more than enough for half a year of drinking water, according to its most recent water management plan. One acre-foot is 325,851 gallons.

SAWS officials have credited the ASR for helping San Antonio get through the drought of 2010-2015 without having to impose more severe stages of water cutbacks.

Finally, there’s the desalination plant that opened in January 2017. At H2Oaks, pumps draw slightly salty water from the Wilcox aquifer and send it through a series of filters and reverse-osmosis membranes, rendering it fresh.

This water goes through the most extensive treatment of any SAWS water source. San Antonio’s municipally owned water and wastewater utility draws water from eight different sources, tapping into every major lake, river, and aquifer in the region.

Edwards water is considered clean enough to deliver without treatment, except for a little chlorine and fluoride.

About 90 percent of the salty water that enters the plant leaves as fresh water, Donat said. What remains is a highly salty brine that’s considered a waste product.

SAWS toyed with several different ways to use this waste product, including an idea to work with a farmer who could use it to raise shrimp, Donat said.

In the end, SAWS got a permit from state regulators to inject it back underground into the Edwards Aquifer, which below H2Oaks is even saltier than the leftover brine.

So why go through all this trouble to tap different aquifers when San Antonio sits right on top of an abundant supply? Before the tour, Haby told visitors about how people who tap the Edwards can pump staggering volumes of water without totally drying it out.

“It’s like pumping out of the ocean,” he said.

It all goes back to eight endangered species –  two salamanders, a tiny crustacean, two beetles, two fish, and a species of wild rice.

These species rely on springs in San Marcos and New Braunfels fed by the aquifer. Heavy pumping of the aquifer might not have completely dried out the aquifer, but it could have dropped water levels low enough to stop the springs from flowing.

That’s why in the 1990s, so the Sierra Club filed a lawsuit to protect the species under the Endangered Species Act.

That lawsuit forever changed San Antonio’s approach to water. The outcome was a limit on how much the aquifer could be pumped so the springs would always remain flowing.

That led San Antonio to embark on a quest for new water supplies that still continues. Its newest water supply will be the 142-mile Vista Ridge pipeline from Burleson County, northeast of Austin, set to begin delivering up to 16.3 billion gallons of water per year starting in 2020.

With so much water set to come from Vista Ridge, SAWS has delayed plans to expand its newest water supply, the desalination plant, Donat said.

Desalination was the main focus of Thursday’s tour, but Donat also pointed out some of artistic and educational features that went into the plant.

Windows into the water testing laboratory, the control room, and an area contacting rows of membrane racks let visitors see how all of the equipment works. Designs on the floor and windows point out the pipes that carry water into and out of the plant, as well as the injection wells off in the distance to dispose of the brine.

Even the building’s design is water-themed. The stone façade incorporates limestone to represent the Edwards and sandstone for the Carrizo and Wilcox aquifers. The bubble-shaped light fixtures inside evoke clouds, and a composite photo mural of splashing water takes up an entire wall near the entryway.

These educational and aesthetic features most impressed R. Brent Locke, a former chair of the Texas Section of the American Water Works Association who was along for the tour.

“Wonderfully done,” he said. “I applaud the effort to make it public-friendly.”

Locke, general manager of Bistone Municipal Water Supply District in the North Central Texas town of Mexia, said water utilities need to do more to “bring the public along” to understand the complexity of the water systems they rely on.

“We need them to discover the value of water,” he said.