AWWA DSS63722

In 1997, the San Antonio Water System (SAWS) began a study to determine the feasibility of developing an aquifer storage recovery (ASR) facility to provide potable water to meet peak seasonal demands and reduce peak withdrawal rates from the Edwards aquifer. The test drilling program suggested that the Carrizo aquifer was suitable for storage of several potential source waters. Also, during the second part of the feasibility investigation, it was determined that the Carrizo aquifer in South Bexar County could provide a substantial supply of new-source groundwater for many years. Therefore, SAWS determined that the development of a conjunctive use project, incorporating an ASR element and a groundwater production element, would be in the interest of San Antonio. This approach provides the most rapid development of the supply source. During the first phase, the ASR system was developed to provide a groundwater supply of 30 million gallons per day (mgd). A total of 17 wells were constructed to supply raw groundwater to a new water treatment plant, pumping station, and transmission pipeline. A bypass around the pumping station and the water treatment plant was constructed to facilitate recharge. Phase 1 is currently operational. Water from these facilities is transported into San Antonio to two terminal points where it is delivered into the SAWS distribution system. Currently, these points are the Seale Pump Station and at the Artesia Pump Station. Additional terminal points are currently under construction for Phase 2. Phase 2 of the ASR Program originally anticipated expansion of the system to 60 mgd of recovery capacity. All Phase 1 facilities were designed to operate at a minimum 60-mgd rate. Planned enhancements necessary to achieve the 60-mgd capacity included construction of up to 17 new ASR wells and the installation of one 20-mgd high service pump at the water treatment plant high service pump station (HSPS). The Carrizo ASR System Capacity Analysis was conducted to define the approximate system capacity for both Phase 1 and Phase 2 conditions, over various operating periods. The system component that limits capacity for each operating period is identified. Results of the Phase 1 analysis provide an estimate of as-built system capacity. The Phase 2 analysis was useful in planning the build-out configuration of the South Bexar County site and in establishing an appropriate design capacity for the Phase 2 expansion. As part of the analysis, the aquifer recharge and recovery capacity for the South Bexar County site currently under SAWS ownership was estimated. The analysis was conducted to provide a planning-level estimate of the ultimate site capacity. A one-year recovery cycle for the Carrizo aquifer was selected for the analysis. Includes reference, tables, figures.