When science, planning, and financing work together April 2017

H2Oaks Center: a water supply success story

When science, planning, and financing work together

With all the economic and population growth Texas continues to experience, the need for innovative approaches to developing and sustaining water supply has never been greater. Water providers throughout the state are taking action, combining innovative science with planning and smart financing to achieve effective solutions for their communities. The Texas Water Development Board (TWDB) is an active partner with many of these communities, providing our scientific and planning expertise and financial assistance to help translate ideas into water flowing through taps.

One of the communities that leads the state in their innovative efforts to develop new water supplies and conserve existing supplies is San Antonio's water utility, the San Antonio Water System (SAWS). When SAWS learned in 1993 that the community would eventually need additional water sources due to mandated Edwards Aquifer withdrawal reductions, the search for other options began. They quickly instituted new conservation programs, which greatly reduced their water use, and within a few years added recycled water. But they also needed to find additional water supplies that could support the city’s long-term needs and population growth. They knew that the process of acquiring and providing water supplies can take years of planning and research before a single shovel of dirt is turned.

In 1996, SAWS began a feasibility study, funded in part by the TWDB, on aquifer storage and recovery (ASR) to determine if ASR could be their next water supply. In ASR, water is injected through a well into an aquifer that acts as an underground storage reservoir. Based on the feasibility study, completed in 1998, SAWS concluded that they could benefit from the use of ASR technology. They next identified and evaluated a series of test wells and then developed prototypical ASR wells—full-sized injection and recovery wells that would confirm full-scale compatibility.

Finally, in 2004 the Twin Oaks ASR facility opened in Bexar County, and since then, SAWS has been collecting excess Edwards Aquifer water during rainy times and storing it in the Carrizo Aquifer for use during our dry Texas summers. In fact, the aquifer is successfully storing approximately 120,000 acre-feet of water, more than three times the amount that was originally projected.

At the time of the ASR opening, SAWS was already planning for their next water supply—brackish desalination. This meant more research on aquifers and well locations as well as pilot wells and a pilot study, and once again the TWDB helped fund one of the studies. It also meant continued engagement in the regional planning process and eventually including a brackish desalination project in their regional water plan.

In addition to financial assistance for the research and studies on brackish desalination, the TWDB provided funding for the construction portion of the plant. In total, SAWS received more than $185 million in financial assistance for the desalination plant from the TWDB over the years. Of that amount, more than $100 million was funding dedicated solely to state water plan projects; the remainder was provided through the TWDB's Drinking Water State Revolving Fund to integrate the plant with other SAWS programs.

The H2Oaks Center (formerly Twin Oaks) opened in early 2017 with the addition of a brackish groundwater desalination plant more than 10 years in the making. Salty water is pumped from 1,500 feet underground in the Wilcox Aquifer and filtered to produce approximately 12 million gallons per day—enough to supply up to 53,000 households. And there's room for future phases to expand this amount.

The Center is now home to three water supplies: desalinated brackish groundwater, aquifer storage and recovery, and fresh water from the Carrizo Aquifer. It's also the only location in the U.S. with three sources of water. Also onsite are educational and research facilities to continue advancing the science related to these topics.

The reality of SAWS' H2Oaks Center was more than 25 years in the making and born out of a need to address short-term water supply needs. Because of the forward-thinking planning, innovative and scientific approaches, and smart financial assistance, it has become so much more. As Robert Puente, president and CEO of SAWS, says, "It is water security for San Antonio's future." And the TWDB is proud to have been a partner along the way.