Carrizo Aquifer Storage and Recovery Project
Long-term Water Supply – a Social and Economic Imperative:
Until recently, the entire San Antonio region relied solely on the Edwards Aquifer for water. However, the San Antonio Water System (SAWS) foresaw the inability of the aquifer to meet future demand, and embarked on a path to integrate alternative water supplies. The Carrizo Aquifer Storage and Recovery (ASR) Program represents a long-term water supply strategy for the San Antonio region. Phase I consists of a new well field in South Bexar County capable of producing 30 million gallons of water per day (mgd) from the Carrizo Aquifer, as well as storing Edwards Aquifer water for later withdrawal during dry times. Phase II of the program increased the capacity of the Edwards storage and recovery system to 60 mgd.
Integration and Image Present Key Challenges:
The 30 mgd Twin Oaks Water Treatment Plant is the first full-process, potable water treatment facility constructed by SAWS. It was designed to treat native Carrizo Aquifer groundwater— removing high levels of dissolved iron, manganese, carbon dioxide and hydrogen sulfide — and to function as a key integration hub for other alternative water supplies. A Texas CEC-member engineering company faced several hurdles, chief among them assuring compatibility of water from the Carrizo with water from the Edwards, and building the Twin Oaks plant on a compressed schedule – without eroding the confidence of SAWS customers who considered Edwards water to be “pristine.”
Source Chemistry, Water quality, and Public Trust:
One of the major challenges faced by the engineers was that the Carrizo water caused corrosion when it was introduced into the SAWS distribution system. Engineers conducted pipe loop simulations of samples from the SAWS distribution system in order to determine the plant treatment process design and mitigate the corrosive effects of Carrizo water on pipes. Although this use of pipe loops to establish plant design is rare, the solution provided by the engineering company has been lauded and studied throughout the water supply industry.
A Compressed Schedule with No Compromises:
SAWS established a compressed, demanding program schedule, requiring the plant design to be completed in nine months — a remarkable timeline for a project as large and complex as Twin Oaks. The schedule, however, did not compromise owner involvement. The design team, owner and program manager fashioned an interactive partnering arrangement to fit the tight schedule so that equipment design, operations, community outreach, architectural development, security and detailed engineering design were nearly simultaneous.
Trusted Engineering Partner Delivers Value:
Despite the unique challenges of the Twin Oaks project, it was completed on time and provides a major step toward a long-term solution to San Antonio water supply needs.
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overall cost and quality. Trust (Look to) the engineering company professionals
to assure quality and true bottom line value in construction.