In June 2018, U.S. Geological Survey (USGS) in cooperation with the U.S. Environmental Protection Agency (EPA) collected geophysical measurements to help evaluate the suitability of a proposed landfill site for disposing mine-waste materials in Fredericktown, MO. Two survey profiles were collected, each including dipole-dipole and Wenner-Schlumberger configurations. For each survey a total of 28 electrodes spaced 1.0 meter (m) apart were used. During the ERT measurement, current is injected through two current electrodes and voltage is measured sequentially across multiple pairs of potential electrodes; the known current and the measured voltages are used to determine the apparent resistivity of the subsurface. Inverse modeling of ERT survey results provide profiles of resistivity that can be interpreted for subsurface layers. This data release provides the raw ERT data and output from inversion.

In June 2017, U.S. Geological Survey (USGS) collected geophysical measurements to help map variations in electrical properties to infer shallow flowpaths and storage zones influenced by residual spilled unconventional oil and gas (UOG). Two survey profiles were collected, each including dipole-dipole and Wenner-Schlumberger configurations. For each survey a total of 56 electrodes spaced 1.0 meter (m) apart were used. During the ERT measurement, current is injected through two current electrodes and voltage is measured sequentially across multiple pairs of potential electrodes; the known current and the measured voltages are used to determine the apparent resistivity of the subsurface. Inverse modeling of ERT survey results provide profiles of resistivity that can be interpreted for subsurface layers. This data release provides the raw ERT data and output from inversion.

In June 2017, U.S. Geological Survey (USGS) collected geophysical measurements to help map variations in electrical properties to infer shallow flowpaths and storage zones influenced by residual spilled unconventional oil and gas (UOG). Two survey profiles were collected, each including dipole-dipole and Wenner-Schlumberger configurations. For each survey a total of 56 electrodes spaced 1.0 meter (m) apart were used. During the ERT measurement, current is injected through two current electrodes and voltage is measured sequentially across multiple pairs of potential electrodes; the known current and the measured voltages are used to determine the apparent resistivity of the subsurface. Inverse modeling of ERT survey results provide profiles of resistivity that can be interpreted for subsurface layers. This data release provides the raw ERT data and output from inversion.

The U.S. Geological Survey, in cooperation with the City of Summerset, South Dakota, performed electrical resistivity tomography (ERT) surveys between July 28 and August 5, 2025. ERT data were collected using an Advanced Geosciences Incorporated SuperSting with 2 passive cables with 14 electrodes per cable. In total, ERT data were collected along 13 transects using 2 passive cables and electrodes spacings of either 1, 2, or 3 meters. Transect lengths varied from 27 to 81 meters. Real time kinematic (RTK) surveys were completed before ERT data collection to obtain latitude, longitude, and elevation of each electrode location. Elevation data collected during RTK surveys were uploaded to EarthImager2D software from Advanced Geosciences, Inc. (https://www.agiusa.com/agi-earthimager-2d) along with apparent resistivity data for inversion. EarthImager2D software allows users to remove noisy measurements either automatically or manually and invert apparent resistivity data to generate two-dimensional profiles of electrical resistivity. Inverted resistivity profiles were generated for all 13 transects. The unprocessed and processed data for each transect are provided as zipped folders (.zip) and annotated accordingly in the metadata. RTK data are provided in a comma separated values (.csv) file.

In October 2016 and May 2017 frequency domain electromagnetic (FDEM) methods were used to image the electrical conductivity of the shallow subsurface. Electrical conductivity can be caused by changes in the soil, overburden, saturation, and water quality. Two multi-frequency tools were used at the site. One of the tools has a 1.6-meter (m) long antenna that was used in the vertical-dipole mode to collect data in stepped-frequency mode at seven user-selected frequencies ranging from 1530 to 47,970 Hertz (Hz). The GEM2HG has an antenna that is 2.1 m long, and it was used in vertical dipole mode with five stepped frequencies ranging from 90 to 24,000 Hz. In general, the lower frequencies penetrate to deeper depths, but the data are an average over a larger volume; whereas higher frequencies penetrate only to shallow depths but provide a smaller volume-averaged measurement. Data were collected at walking speeds of 3 kilometers per hour (km/hr), with a full suite of seven frequencies measured every 0.5 seconds (s), which translates to a complete measurement suite about every 0.4 m along the profile. All measurements were georeferenced with a global positioning system (GPS). Both the primary and secondary fields were measured at the receiver coil, and the ratio of the secondary to primary magnetic fields was recorded as in-phase and quadrature. The in-phase part of the EM field relates to the magnetic susceptibility, and the quadrature component relates to apparent conductivity (aEC) . Raw data for each frequency and Q Sum (a summation of quadrature values) were recorded in parts per million (ppm). In post processing, EM data were converted to magnetic susceptibility and aEC, which can be inverted to get the actual depth of the electrical conductivity value. This data release provides the raw ppm values, the magnetic susceptibility, and the apparent electrical conductivity values.

The Cahuilla Valley and Terwilliger Valley groundwater basins, 9-006 and 7-026 respectively (California Department of Water Resources 2016) located approximately 25 miles southwest of Palm Springs, are the sole-source for groundwater supply for the rural disadvantaged community and two Native American Tribes, the Ramona Band of Cahuilla and the Cahuilla. The characteristics and sustainable yield of the Cahuilla Valley and Terwilliger Valley groundwater basins are not well understood and are threatened by increasing water use and potential changes in water sustainability related to climate change. Previous USGS studies of the Cahuilla-Terwilliger Valley groundwater basins defined the thicknesses and characteristics of the alluvial sediments that constitute the main water-bearing unit of the aquifer system and identified where wells completed in the underlying fractured bedrock are located (Moyle, 1976; Landon and others, 2015; Woolfenden and Bright, 1988). However, although the fractured bedrock is an important part of the aquifer system for domestic and some irrigation supply, the thickness and hydraulic characteristics of the fractured bedrock are not well understood (Landon and others, 2015; Moyle 1976). Existing gravity data identified a possible conduit for groundwater flow beneath Cahuilla Creek in the Cahuilla and Durasno Valleys (Landon and others, 2015). Electrical resistivity tomography (ERT) data was collected in August 2018 to evaluate the cross-sectional depth to bedrock underlying a narrow section of Durasno Valley, and to help select locations for groundwater monitoring wells. Data from two transects were collected perpendicular to Cahuilla Creek, and offset by approximately 600 meters (m).

The Cahuilla Valley and Terwilliger Valley groundwater basins, 9-006 and 7-026 respectively (California Department of Water Resources 2016) located approximately 25 miles southwest of Palm Springs, are the sole-source for groundwater supply for the rural disadvantaged community and two Native American Tribes, the Ramona Band of Cahuilla and the Cahuilla. The characteristics and sustainable yield of the Cahuilla Valley and Terwilliger Valley groundwater basins are not well understood and are threatened by increasing water use and potential changes in water sustainability related to climate change. Previous USGS studies of the Cahuilla-Terwilliger Valley groundwater basins defined the thicknesses and characteristics of the alluvial sediments that constitute the main water-bearing unit of the aquifer system and identified where wells completed in the underlying fractured bedrock are located (Moyle, 1976; Landon and others, 2015; Woolfenden and Bright, 1988). However, although the fractured bedrock is an important part of the aquifer system for domestic and some irrigation supply, the thickness and hydraulic characteristics of the fractured bedrock are not well understood (Landon and others, 2015; Moyle 1976). Existing gravity data identified a possible conduit for groundwater flow beneath Cahuilla Creek in the Cahuilla and Durasno Valleys (Landon and others, 2015). Electrical resistivity tomography (ERT) data was collected in August 2018 to evaluate the cross-sectional depth to bedrock underlying a narrow section of Durasno Valley, and to help select locations for groundwater monitoring wells. Data from two transects were collected perpendicular to Cahuilla Creek, and offset by approximately 600 meters (m).

The Cahuilla Valley and Terwilliger Valley groundwater basins, 9-006 and 7-026 respectively (California Department of Water Resources 2016) located approximately 25 miles southwest of Palm Springs, are the sole-source for groundwater supply for the rural disadvantaged community and two Native American Tribes, the Ramona Band of Cahuilla and the Cahuilla. The characteristics and sustainable yield of the Cahuilla Valley and Terwilliger Valley groundwater basins are not well understood and are threatened by increasing water use and potential changes in water sustainability related to climate change. Previous USGS studies of the Cahuilla-Terwilliger Valley groundwater basins defined the thicknesses and characteristics of the alluvial sediments that constitute the main water-bearing unit of the aquifer system and identified where wells completed in the underlying fractured bedrock are located (Moyle, 1976; Landon and others, 2015; Woolfenden and Bright, 1988). However, although the fractured bedrock is an important part of the aquifer system for domestic and some irrigation supply, the thickness and hydraulic characteristics of the fractured bedrock are not well understood (Landon and others, 2015; Moyle 1976). Existing gravity data identified a possible conduit for groundwater flow beneath Cahuilla Creek in the Cahuilla and Durasno Valleys (Landon and others, 2015). Electrical resistivity tomography (ERT) data was collected in August 2018 to evaluate the cross-sectional depth to bedrock underlying a narrow section of Durasno Valley, and to help select locations for groundwater monitoring wells. Data from two transects were collected perpendicular to Cahuilla Creek, and offset by approximately 600 meters (m).

The Cahuilla Valley and Terwilliger Valley groundwater basins, 9-006 and 7-026 respectively (California Department of Water Resources 2016) located approximately 25 miles southwest of Palm Springs, are the sole-source for groundwater supply for the rural disadvantaged community and two Native American Tribes, the Ramona Band of Cahuilla and the Cahuilla. The characteristics and sustainable yield of the Cahuilla Valley and Terwilliger Valley groundwater basins are not well understood and are threatened by increasing water use and potential changes in water sustainability related to climate change. Previous USGS studies of the Cahuilla-Terwilliger Valley groundwater basins defined the thicknesses and characteristics of the alluvial sediments that constitute the main water-bearing unit of the aquifer system and identified where wells completed in the underlying fractured bedrock are located (Moyle, 1976; Landon and others, 2015; Woolfenden and Bright, 1988). However, although the fractured bedrock is an important part of the aquifer system for domestic and some irrigation supply, the thickness and hydraulic characteristics of the fractured bedrock are not well understood (Landon and others, 2015; Moyle 1976). Existing gravity data identified a possible conduit for groundwater flow beneath Cahuilla Creek in the Cahuilla and Durasno Valleys (Landon and others, 2015). Electrical resistivity tomography (ERT) data was collected in August 2018 to evaluate the cross-sectional depth to bedrock underlying a narrow section of Durasno Valley, and to help select locations for groundwater monitoring wells. Data from two transects were collected perpendicular to Cahuilla Creek, and offset by approximately 600 meters (m).

The Cahuilla Valley and Terwilliger Valley groundwater basins, 9-006 and 7-026 respectively (California Department of Water Resources 2016) located approximately 25 miles southwest of Palm Springs, are the sole-source for groundwater supply for the rural disadvantaged community and two Native American Tribes, the Ramona Band of Cahuilla and the Cahuilla. The characteristics and sustainable yield of the Cahuilla Valley and Terwilliger Valley groundwater basins are not well understood and are threatened by increasing water use and potential changes in water sustainability related to climate change. Previous USGS studies of the Cahuilla-Terwilliger Valley groundwater basins defined the thicknesses and characteristics of the alluvial sediments that constitute the main water-bearing unit of the aquifer system and identified where wells completed in the underlying fractured bedrock are located (Moyle, 1976; Landon and others, 2015; Woolfenden and Bright, 1988). However, although the fractured bedrock is an important part of the aquifer system for domestic and some irrigation supply, the thickness and hydraulic characteristics of the fractured bedrock are not well understood (Landon and others, 2015; Moyle 1976). Existing gravity data identified a possible conduit for groundwater flow beneath Cahuilla Creek in the Cahuilla and Durasno Valleys (Landon and others, 2015). Electrical resistivity tomography (ERT) data was collected in August 2018 to evaluate the cross-sectional depth to bedrock underlying a narrow section of Durasno Valley, and to help select locations for groundwater monitoring wells. Data from two transects were collected perpendicular to Cahuilla Creek, and offset by approximately 600 meters (m).