Water level, water temperature, and specific conductance data collected during natural gradient tests in observation wells set in the upper transmissive zone of the Ogallala Aquifer, North East 2nd Street Superfund Site, Happy, Texas, 2023

Water level, water temperature, and specific conductance data were collected during natural gradient tests on six observation wells screened in the upper transmissive zone of the Ogallala aquifer at the North East 2nd Street Superfund site in Happy, Texas, from November 6-13, 2023. Tests involved gravity draining 100-160 gallons of a low-concentration salt-spiked solution with an associated specific conductance of less than 8,000 microsiemens per centimeter (µs/cm) into the wells, measuring water level responses, and recording continuous downhole water temperature and water conductivity (specific conductance). Gravity drainage of the salt-spiked solution into each well took approximately 1 hour at average rates of 2.4 to 5.2 gallons per minute. Depth profiles of water temperature and specific conductance were collected under ambient conditions (prior to draining the salt-spiked solution into each well). Another depth profile was collected after the salt-spiked solution was added to each well (to identify vertical changes in the water column of the well and the degree of vertical mixing of the spiked water). The single well natural gradient tests allow for the analysis of hydraulic responses of the aquifer during gravity drainage and assessment of ambient flow through the well after the emplacement of the salt-spiked solution and subsequent flushing out of the solution back to ambient conditions. Monitoring at each well continued for at least 24 hours after gravity-drainage of the salt-spiked solution into each well was completed to ascertain whether background conditions were achieved. This data release contains information on the well construction of the six wells tested in 2023 for natural gradient tests, the volume and concentration of the dilute salt spike used, profiles of specific conductance and water temperature of the wells pre- and post-spiked, water levels, and continuous monitoring of specific conductance and water temperature.