Unlock the Opportunity!—A Re-Evaluation of the Lower Trinity Aquifer in Central Texas

Prolonged drought and regulatory limitations on groundwater production have forced entities to explore alternative sources for water. Recent drilling and successful completion of new production wells to depths as great as 2850 feet in the Central Texas area has revealed that the Lower Trinity Aquifer is much more productive than previously thought and as modeled by the Texas Water Development Board. Examination of drill cuttings from this aquifer revealed thick gravel beds near the base of the formation along with intervals of interbedded coarse sand. The inspection of drill cuttings and subsequent evaluation of geophysical logging aided us in locating these favorable water-bearing zones. One of the production wells we will discuss in our presentation was completed with 342 feet of screen placed within these sand and gravel beds of the Lower Trinity Aquifer. After well completion, a single-well pumping test was conducted to evaluate the aquifer hydraulic properties at the well site. The production testing revealed that the hydraulic conductivity is more than an order of magnitude higher at this site than what is represented in the existing aquifer model used by the state for regulatory decisions. In addition, the thickness of the aquifer is greater than what has previously been reported and modeled. The hydrogeologic information recently collected from the drilling and testing program may unlock the opportunity for producing large water supplies to help meet the demands of this rapidly growing area. This presentation will provide a review of the information collected along with our interpretation of the data and the implications for assessing groundwater availability for the future from this prolific aquifer.