Aquifer Beaker

Edwards Aquifer

Aquifer Level 685.4'
1/19/17 - Official

The Edwards aquifer and its catchment area in the San Antonio region is about 8,000 square miles and includes all or part of 13 counties in south-central Texas.

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Year-Round Watering Hours

Watering with an irrigation system or sprinkler is allowed any day of the week before 11 a.m. or after 7 p.m.

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Aquifer Level 685.4 | Year-Round Watering Hours

eBill Site Maintenance

4 - 6:00 a.m.

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Brackish Groundwater - Desalination

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 12 million gallons of water per day (mgd) or 13,440 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 30 mgd or 33,600 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 $411.4 million. The cost per acre-foot of all three phases of the program is estimated at $1,138.

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.

Click to get a 360 view of SAWS Desalination plant in the final construction phase and nearing completion late this fall.

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

Making the
Program Possible
The 2007 Texas Legislature played a pivotal role in the development of our desalination program.
House Bill 1886 allows Texas municipalities to utilize the Construction Manager at Risk (CMAR) procurement method for water supply projects. Use of CMAR procurement can help reduce construction time and costs, as well as allow greater collaboration between the design, contracting and in-house teams.
In addition, House Bill 2654 provides for a general permit for Class I injection wells that can be used to dispose of brine concentrate from a municipal desalination plant. The new permit process will greatly reduce the time required for the authorization of Class I injection wells.

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 12 Wilcox production wells have been drilled. The depths for the production wells range from 1,200 to 1,800 feet. 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 Black & Veatch as the program manager to perform pre-conceptual design services for the brackish groundwater desalination program. In January 2013, SAWS awarded the design contract to Black & Veatch in order to manage and perform the design of the brackish groundwater desalination program.
  • Construction Manager at Risk: In December 2012, SAWS selected Zachry-Parsons Water Resources Joint Venture to be the construction manager at risk for the desalination program. The construction manager will provide design review, constructability review and construction management for the brackish groundwater desalination program.
  • Guaranteed Maximum Price: A guaranteed maximum price submitted by Zachry-Parsons Water Resources Joint Venture was approved by SAWS Board of Trustees in March 2014 to construct the remaining components of the brackish groundwater desalination program.

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