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Hydrogeology of the Saline Edwards Zone, Southeast Travis County, Central Texas

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Hydrogeology of the Saline Edwards Zone, Southeast Travis County, Central Texas Hydrogeology of the Saline Edwards Zone, Southeast Travis County, Central Texas BSEACD Report of Investigations 2017-1015 October 2017 Barton Springs/Edwards Aquifer Conservation District 1124 Regal Row Austin, Texas Disclaimer All of the information provided in this report is believed to be accurate and reliable; however, the Barton Springs/Edwards Aquifer Conservation District and the authors assume no liability for any errors or for the use of the information provided. This report documents data collection, evaluation, and interpretation performed by geoscientists licensed by the Texas Board of Professional Geoscientists (TBPG). Geochemical evaluations and interpretation were performed by a licensed geoscientist of the Texas Board of Professional Geoscientists (TBPG). Cover Page: Drilling of saline Edwards multiport well and pond with produced waters. Photograph taken August 2016. BSEACD Report of Investigations 2017-1015 i | Page Hydrogeology of the Saline Edwards Zone, Southeast Travis County, Central Texas Brian A. Smith, Ph.D., P.G., and Brian B. Hunt, P.G. Barton Springs/Edwards Aquifer Conservation District Bruce Darling, Ph.D., P.G. Groundwater & Geochemical Consulting, LLC BSEACD General Manager John Dupnik, P.G. BSEACD Board of Directors Mary Stone Precinct 1 Blayne Stansberry, President Precinct 2 Blake Dorsett Precinct 3 Dr. Robert D. Larsen Precinct 4 Craig Smith, Vice President Precinct 5 BSEACD Report of Investigations 2017-1015 October 2017 Barton Springs/Edwards Aquifer Conservation District 1124 Regal Row Austin, Texas BSEACD Report of Investigations 2017-1015 ii | Page Contents Summary ....................................................................................................................................................... 1 Introduction .................................................................................................................................................. 3 Study Area ..................................................................................................................................................... 3 Geology ......................................................................................................................................................... 5 Structure ................................................................................................................................................... 5 Hydrogeology ................................................................................................................................................ 8 Saline Edwards Aquifer ................................................................................................................................. 8 Freshwater/saline-water Interface ........................................................................................................... 9 Source of Saline Water............................................................................................................................ 10 Saline Edwards Groundwater Availability ................................................................................................... 11 Saline Edwards Multiport Monitor Well ..................................................................................................... 14 Stratigraphy ................................................................................................................................................. 15 Previous Work ......................................................................................................................................... 15 Results: Stratigraphy ............................................................................................................................... 15 Results: Multiport Well Design ............................................................................................................... 18 Discussion: Stratigraphy and Multiport Well Design .............................................................................. 18 Water Levels and Hydraulic Gradients ........................................................................................................ 25 Previous work ......................................................................................................................................... 25 Methods .................................................................................................................................................. 26 Results: Water Levels and Hydraulic Gradients ...................................................................................... 27 Discussion: Water-Level and Gradient Data ........................................................................................... 32 Aquifer Parameters ..................................................................................................................................... 32 Previous work ......................................................................................................................................... 32 Methods .................................................................................................................................................. 32 Results: Hydraulic Conductivity .............................................................................................................. 36 Well Yield Estimates ................................................................................................................................ 36 Discussion of Permeability ...................................................................................................................... 38 Geochemistry .............................................................................................................................................. 38 Previous work ......................................................................................................................................... 38 Methods .................................................................................................................................................. 39 Results: Geochemistry ............................................................................................................................ 39 Equilibrium Chemistry ............................................................................................................................. 41 BSEACD Report of Investigations 2017-1015 iii | Page Origin of Salinity ...................................................................................................................................... 49 Discussion of Geochemistry Data ........................................................................................................... 53 Conclusions ................................................................................................................................................. 54 Future Studies ............................................................................................................................................. 55 Acknowledgements ..................................................................................................................................... 55 References .................................................................................................................................................. 56 Supplemental Information Available Upon Request .................................................................................. 61 Aerial photograph of the multiport well (right side) and the water-holding tanks containing all produced water. Photo taken 11/2/2016. BSEACD Report of Investigations 2017-1015 iv | Page Hydrogeology of the Saline Edwards Zone, Southeast Travis County, Central Texas Brian A. Smith, Ph.D., P.G., and Brian B. Hunt, P.G. Barton Springs/Edwards Aquifer Conservation District Bruce Darling, Ph.D., P.G. Groundwater & Geochemical Consulting, LLC Summary Increased demand for water in central Texas is causing water users and providers to look for additional sources of water. The saline portion of the Edwards Aquifer (saline Edwards Aquifer) has often been mentioned as a source of water for desalination or aquifer storage and recovery (ASR). The resource has not previously been considered by large water suppliers because of limitations of data, regulatory framework, and fear of saline encroachment into the freshwater Edwards. Recent legislative efforts combined with hydrogeologic and engineering studies have renewed interest in the saline Edwards Aquifer. This report documents a hydrogeologic study conducted by the Barton Springs/Edwards Aquifer Conservation District (District) of the saline Edwards Aquifer in southeastern Travis County providing baseline information for an engineering study of desalinization and ASR. This hydrogeologic study is part of an engineering study is conducted by Carollo Engineers, Inc. and is partially funded by a Texas Water Development Board (TWDB) regional facility planning grant and the District. In August 2016, a multiport monitor well was installed to a depth of 1,100 ft through the entire saline Edwards Aquifer with 18 permanently isolated zones from which head, water chemistry, and permeability data can be collected. Four zones were completed in the units overlying the Edwards Group and 14 zones were completed within the Edwards and associated units. Data collected in the multiport well allow for the detailed hydrogeologic
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