Feasibility Study and Pilot Test of Aquifer Storage and Recovery, Texas
Challenge: Develop and install an ASR well in the highly regulated Edwards Aquifer in Texas
Solution: INTERA is part of a team performing a phased ASR demonstration project for NBU, with the potential for a full buildout with 10 to 20 wells. NBU determined that ASR is the most cost-effective option for increasing the reliability and resiliency of their water supply. During periods of high surface water availability or low water demand, ASR allows storage that can subsequently be retrieved during periods of low surface water availability or high demand. In the first phase, we provided hydrogeologic support for the ASR feasibility study. This included identifying the brackish portion of the Edwards Aquifer as a potential storage zone for ASR. During the pilot phase, INTERA designed a monitor well and an associated aquifer testing program to determine water quality in the brackish Edwards Aquifer, and potential productivity of the upper and lower Edwards. We supervised the drilling, directed the hydraulic testing (including specific capacity and spinner logging), and collected water quality samples from the monitor well. INTERA has also designed additional monitor wells and collaborated on the design of the pilot phase test well. Finally, INTERA supervised the drilling, installation, and hydraulic testing of the ASR pilot well.
In addition, two key regulatory challenges were identified and addressed with respect to this ASR project. First, the Edwards Aquifer Authority (EAA) was concerned about any potential effect ASR may have on an important nearby spring, Comal Springs. Second, EAA rules did not allow recharge of water other than unaltered Edwards Aquifer groundwater. To address concerns about Comal Springs, NBU and EAA formed an Interlocal Agreement Workgroup for monitoring and managing any potential changes to Edwards Aquifer water levels or water quality due to ASR. INTERA served as a key participant in this Workgroup. To overcome the second regulatory challenge, INTERA, Arcadis, and ASR Systems supported NBU in getting legislation passed that changed EAA rules to allow recharge of treated surface water from an ASR system as long as it occurs in a brackish potion of the aquifer.