The purpose of the surveys was to 1. locate the precise location of submerged conduits carrying flow to Main Barton Springs on the north and south banks of the Barton Springs pool, 2. characterize the hydraulic relation between the Main Barton, Old Mill and Eliza Springs, 3. determine the potential location of caves and active flow paths beneath the three springs, and 4. characterize the geophysical signatures of the fault crossing the Barton Springs pool. The geophysical surveys revealed three general types of anomalies. Resistivity results from the south of the Barton Springs swimming pool indicate presence of a thick, laterally extensive high conductivity layer above the pool elevation. This high conductivity layer is interpreted to be lateral clay deposits, either associated with the Del Rio clay or clay-rich alluvial deposits associated with Barton Creek. These clay layers appear to overlie the Edwards Aquifer south of the pool.
Also south and east of the pool are cylindrical high conductivity anomalies that extend deeper than the elevation of the submerged cave observed in Barton Springs pool. These cylindrical high conductivity anomalies are also associated with NP anomalies, suggesting groundwater flow. One hypothesis is that the alignment of the high conductivity and NP anomalies corresponds to the Saline-Line Flow Route that is known to discharge primarily at Old Mill Springs, and is hydraulically connected to Main Barton Springs and Eliza Springs. This hypothesis is favored because the Saline-Line Flow Route carries relatively mineralized groundwater and is known to connect to Old Mill Springs and at some times Main Barton and Eliza Springs. There are likely several conduit paths to the pool from the southern part of Zilker Park. An air-filled train tunnel corresponded to a high-resistivity anomaly. Local utility lines crossing the site showed no significant resistivity anomaly but metal pipes were detectable with EM conductivity surveys.
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