San Antonio Water System Brackish Groundwater Desalination (BGD) Program

Challenge

To reduce dependency on the Edwards Aquifer, the main water supply source for nearly 1.6 million in San Antonio, Texas, officials with the San Antonio Water System (SAWS) approved a unique brackish groundwater desalination program as part of its overall 2012 water management plan. Located in the southern Bexar County region, this previously untapped water source of brackish groundwater will both diversify and meet regional water needs over the next 50 years. Once treated, the brackish groundwater will augment current surface water sources with production of 30 million gallons per day (mgd).

Approach

As the CMAR firm for the project, Parsons Environment & Infrastructure Group, Inc. and its joint venture partner constructed the first portion of this critical brackish groundwater desalination (BGD) program. Projected to cost $119 million, the project includes: a 12-mgd reverse osmosis membrane water treatment plant, 12 raw water production wells, raw and finished water conveyance, residual conveyance, a new deep injection well, a chemical treatment system, supervisory and data acquisition controls, and a new administration building.

Using a unique milestone constructibility review and cost-estimate process, Parsons collaborated with designers to adapt alternative construction methods, resulting in substantial cost savings. The permit team—consisting of experts from SAWS, Parsons, and its JV partner—worked quickly to obtain needed environmental and construction permits and avoid delays.

To address complex soil conditions that can lead to borehole instability, a construction method that uses polymer slurry for the drilled pier foundations kept the borehole stable for the entire depth of the excavation. Reinforcing steel was then placed into the slurry and concrete injected from a pump beginning at the bottom of the excavation.

Creating individual work packages for the early critical-path scopes involved coordinating multiple complex tasks—which included integrating smaller subcontract firm participation and an accelerated work schedule—but also provided more and greater opportunities for local firms to participate in the project.

A significant factor in any project is its safety program  — which is designed to be proactive and interactive in order to achieve a safety goal of zero incidents. The SAWS project safety program includes: daily “Take 5” meetings, weekly safety meetings, monthly mass safety meetings, and a host of safety related items resulting in a record of zero lost time to date, not only meeting the target milestones, but also exceeding all quality standards.

Results

SAWS’ BGD plant generates approximately 6 million gallons of water per day, or 13,440 acre-feet per year, from the Wilcox Aquifer. The project’s (SMBE/SWBE) program maximizes participation and promotes equal opportunity and has exceeded SAWS’ goal of awarding 17% to SMBEs/SWBEs with 36.4% participation.

“San Antonio Water System (SAWS) is proud to have partnered with Parsons and their joint venture partner (JV) for this critical CMAR project. Constructing the 12-mgd brackish water desalination plant is momentous for SAWS and the citizens of San Antonio and must be executed flawlessly. Currently we are under Level 2 water restrictions, so tapping into the groundwater resource for much needed drinking water is vital to our region.

We are very pleased to report that the project has maintained a record of zero lost time to date due to the Parsons’ JV’s commitment to safety and implementing an exceptional health and safety program. Further, Parsons’ JV has exceeded SAWS SMBE/SWBE participation goals of 17 percent overall with 36.4 percent participation and the project is only 68 percent complete. If the project continues on this path, we anticipate it will meet all schedule milestones.”
– Esther Harrah, Project Manager, San Antonio Water System

“Parsons is pleased to be collaborating on this important project that advances SAWS’ sustainable water supply strategy by preserving potable groundwater aquifers and employing reverse osmosis membrane technology to desalinate previously untapped brackish groundwater.”
Virginia Grebbien, Parsons Group President