Estimation of hydraulic properties in the Ogallala aquifer near Happy, Texas from slug test results at the North East 2nd Street Superfund site, U.S. Geological Survey data release

The North East 2nd Street Superfund site in Happy, Texas, overlies a groundwater plume of primarily carbon tetrachloride (CT) that is contained within an upper transmissive zone (EA Engineering, Science, and Technology, Inc., 2019) of the Ogallala aquifer. The Ogallala aquifer is contained at the site in Tertiary-age sediments of the Ogallala Formation, which are described by Nordstrom and Fallin (1989, p.10) as "tan, yellow, and reddish-brown, silty to coarse-grained sand mixed or alternating with yellow to red silty clay and variable sized gravel." The plume originated from the application of fire-retardant chemicals to the ground surface during the extinguishing of a fire at a grain storage elevator in 1962. As of 2022, the CT plume was 60 years old and extended approximately two thirds of a mile downgradient (northeast) from the site of the fire along a sloping clay bed. No hydraulic controls or boundaries are evident at the leading edge of the plume to constrain its further transport, and center-pivot irrigated agriculture and concentrated animal feeding operations are immediately downgradient across Interstate Highway 27. Because minimal sampling data have been collected, the question of whether the plume has reached a state of equilibrium is unknown. Slug tests were performed at 14 monitoring wells during February 7–9, 2023, near the North East 2nd Street Superfund site to characterize the range and distribution of hydraulic conductivity values in the upper transmissive zone of the Ogallala aquifer. Estimated hydraulic conductivities ranged from 0.27 to 12.97 ft/day, with the two northernmost wells (MW-27 and MW-28) tested exhibiting the lowest values.