Your Water
Brackish Groundwater Desalination
Developing an untapped resource for the benefit of the entire region
San Antonio Water System is currently developing a brackish groundwater desalination program in southern Bexar County. Brackish groundwater is a plentiful, previously untapped local source of water that will help diversify San Antonio's supplies.
SAWS future desalination facility will generate about 11 million gallons of water per day (mgd) or 12,210 acre-feet per year from the Wilcox Aquifer in Phase I. The plant will be located at the existing SAWS Twin Oaks Aquifer Storage & Recovery site.
The well sites will be located on adjacent SAWS property. Phases II and III will be completed in 2021 and 2026 respectively and will deliver a total of more than 27 mgd or 30,525 acre-feet per year. The total capital costs of the program for all three phases, including land acquisition, feasibility, design, construction and SAWS overhead is currently estimated at about $297 million. The cost per acre-foot of all three phases of the program is estimated at $1,003.
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Project Overview
The brackish desalination program is part of the SAWS 2012 Water Management Plan, designed to meet the city's water needs over the next 50 years while reducing dependence on the Edwards Aquifer. The Texas Water Development Board has confirmed that a vast supply of brackish groundwater – water too salty to drink – exists in our region and has yet to be developed.
The South Central Regional Planning Group (Region L) has identified brackish groundwater as a supply management strategy to meet future needs.
Initial Investigations
Feasibility studies confirm that there is sufficient quantity and quality of brackish groundwater available in the Wilcox Aquifer to support the SAWS desalination program. Brackish water, which contains dissolved solids, will be treated to drinking standards using a reverse osmosis treatment facility.
Brackish water in the Wilcox is expected to range from 1,300-1,500 mg/L Total Dissolved Solids. Pilot testing confirms that reverse osmosis treatment is suitable for the SAWS program. In addition, SAWS has completed tests and studies to define:
- Well field productivity
- Long-term water quality
- Treatment plant operation
- Pre-treatment and post-treatment requirements
- Concentrate disposal (Deep Well Injection)
Program Development
The proposed desalination facility location at the Twin Oaks Aquifer Storage & Recovery site is close to the brackish water source and also near the proposed areas for brine disposal.
The first phase of the program includes development of a production well field, well field collection system and reverse osmosis treatment plant. Brine disposal will be accomplished through the use of Class I injection wells located on SAWS property in nearby Wilson County. The treatment facility also will be designed to accommodate additional capacity and technology upgrades in the future.
Other engineering and construction components include:
- Geotechnical testing
- Site work preparations
- Administrative building
- Laboratory, treatment and storage buildings
- Well pumps
- Paved access roads
- On-site yard piping
Phase I is expected to be complete in 2016.
Program Update
As the program progresses, SAWS has participated in the following activities to support the future design, construction and operation of the brackish desalination program:
- Land Acquisition: In 2010, SAWS acquired the remaining property to support production wells for Phase I of the program.
- Production Wells: Eight of 13 Wilcox production wells are anticipated to be drilled in 2011-2012. These wells will assist in the design and construction of the brackish desalination program by providing additional information such as production rates and water quality.
- Injection Well Testing: SAWS has completed the drilling and testing of a concentrate disposal well into the Edwards Formation. Results from this test well will supply water quality, depth, injection pressures and characteristics of the disposal formation. This information will assist in the permitting, design and construction of the remaining injection wells.
- Additional Membrane Pilot Testing: In 2010, the Texas Commission on Environmental Quality (TCEQ) approved the first Membrane Pilot Study report. In 2011, SAWS performed in-house piloting on two additional membranes that could be used in the full-scale plant. These were approved by the TCEQ in October 2012. Testing and approval of three reverse osmosis membranes by TCEQ will create a more competitive environment for purchasing when the plant becomes operational.
- Program Manager: In early 2012, SAWS hired a program manager to perform pre-conceptual design services for the brackish groundwater desalination program. In December of 2012, SAWS will award the design contract to the program manager in order to manage and perform the design of the brackish groundwater desalination program.
- Construction Manager at Risk: SAWS is currently evaluating proposals for a construction manager at risk. The construction manager will provide design review, constructability review, and construction management for the brackish groundwater desalination program. The anticipated award date for the construction manager at risk is December 2012.
Contracting Opportunities
The brackish desalination program will produce a variety of opportunities for companies to work with SAWS, including Small, Minority and Women-owned Businesses (SMWB). Companies may register to be informed of contracting opportunities, as well as availability of plans and specifications for SAWS projects.
Visit our SMWB program page for more information.
* An acre-foot of water is equivalent to 325,851 gallons
