Bennett E. Hoogenboom Justine M. Overacker Meghan C. Dick Christopher P. Ely Allen H. Christensen 20251219 tabular digital data; shapefile https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/P16PH76Q Surface electrical resistivity tomography (ERT) data were acquired December 2 - 5, 2024 by the U.S. Geological Survey (USGS) at the San Gorgonio Pass Water Agency's Brookside West site in Beaumont, California. The purpose of this survey was to map near surface geologic structure in an area that the San Gorgonio Pass Water Agency plans to develop as a managed aquifer recharge site. Three ERT profiles were acquired at depths up to 50 meters (m) using the Advanced Geosciences, Inc. SuperSting R8 resistivity meter. This data release includes the raw and processed resistivity data as well as inverted resistivity models. All data are provided as digital data, and data fields for each file type are defined in the respective data dictionary. These surface data were collected to contribute high-resolution information about subsurface geologic structure related to understanding fault structures and surface water recharge potential in the area. 20241202 20241205 ground condition Complete None planned -116.990100 -116.982600 33.960200 33.949100 ISO 19115 Topic Category geoscientificInformation environment USGS Thesaurus electrical resistivity imaging electromagnetic surveying geophysics hydrogeology geospatial datasets engineering sciences water resources groundwater surface water (non-marine) None electrical resistivity tomography ERT surveying resistivity electromagnetics California Water Science Center U.S. Geological Survey USGS Metadata Identifier USGS:680ed046d4be024491bea15e Geographic Names Information System (GNIS) Beaumont, CA San Gorgonio Pass Riverside County Noble Creek None. Please see 'Distribution Information' for details. These data are marked with a Creative Common CC0 1.0 Universal License. These data are in the public domain and do not have any use constraints. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. It is requested that the suggested citation for this USGS data release be included in any publications that reference or utilize these data. Bennett E. Hoogenboom U.S. Geological Survey, California Water Science Center Geophysicist mailing and physical address

6000 J Street, Placer Hall, CAWSC

Sacramento CA 95819 United States 916-278-3000 bhoogenboom@usgs.gov Funding was provided by San Gorgonio Pass Water Agency Esri ArcGIS Pro v. 3.3.1; Advanced Geosciences Inc. EarthImager 2D v. 2.4.4.649; Microsoft Excel for Microsoft 365 MSO Version 2507 Build 16.0.19029.20136 No formal attribute accuracy tests were conducted. Survey line names were assigned during data acquisition. Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. No formal attribute accuracy tests were conducted. No formal positional accuracy tests were conducted. The USGS conducted the electrical resistivity tomography (ERT) survey from December 2 - 5, 2024. Three two-dimensional lines were acquired, named Lower Creek (LW_CREEK), Upper Creek (UP_CREEK), and Up Land (UP_LAND). Dipole-dipole array and strong-gradient array data were acquired on all lines. A maximum of 56 stainless steel electrodes were deployed in a single layout. A dilute salt solution mixed with kitty litter and underlain by aluminum foil sheets was added to the base of the electrodes to reduce the contact resistance. The acquisition parameters include: 3,000 milliAmp (mA) maximum current, 1,250 millisecond (msec) measurement time, three measurement cycles, 4 percent root-mean-square (RMS) error threshold, and a maximum of two repeat measurements. Raw data files are provided in Advanced Geosciences, Inc. (AGI) *.stg formatted ASCII, comma-separated files, and file format descriptions are provided in the associated data dictionary. Spatial locations of all electrodes were measured with a Trimble Geo 7X global navigation satellite system (GNSS) device. 20241203 Raw data, located in the Raw_Data folder, were imported from 6 files into the AGI EarthImager 2D software (Advanced Geosciences, Inc., Austin, Texas, USA) for processing and inversion. For a given line, measurements from the strong-gradient and dipole-dipole surveys are combined during the inversion process to create a single profile per line. Robust inversions with horizontal/vertical roughness ratios of 1.0 were run for all 3 profiles. These inversions included terrain with smoothness and damping factors of 10 and data and model conditioners of 1. Each profile required data culling based on data misfit to reduce the overall RMS misfit of the models (indication of the predicted forward response to final inverted models fit to measured observations). Data misfit percentage thresholds were chosen based on a balance of improving the model misfit and maintaining adequate data coverage across the profiles. Final inverted model misfit values: LWCREEK: 4.62 percent RMS and 2.34 L2 norm, UPCREEK: 2.77 percent RMS and 0.85 L2 norm, UPLAND: 2.84 percent RMS and 0.89 L2 norm. The final model parameters described above were selected because they best represent the physical understanding of the system and minimized data misfit. Final inverted resistivity model and model sensitivity data were exported to *.dat and *.bln ASCII grids. 20250429 Final smooth resistivity models, model sensitivity, and georeferenced coordinate data were combined to generate a single georeferenced output resistivity model file in the project projection system in ASCII .csv format to meet open data requirements. The sensitivity mask (sm) represents the inverse relation between model sensitivity and depth. It is estimated from normalized model sensitivities calculated from the inversion process. The sensitivity mask is an approximation for depth of investigation, with near surface values equaling ~1, and total model depth equaling ~0. It is calculated using the normalized model sensitivity (NormSens) and an exponential decay to represent depth following this formula: Sens_mask=[exp(1.1*(log10(NormSens) + 1.3))]. 20250429 Geographic information system feature layer shapefiles of the survey locations were developed from the spatial information for the ERT data. Survey line names are retained with the shapefile. 20250429 Point Point 189 Universal Transverse Mercator 11 0.9996 -117.0 0.0 500000.0 0.0 coordinate pair 0.6096 0.6096 meters NAD83_National_Spatial_Reference_System_2011 GRS 1980 6378137.0 298.257222101 North American Vertical Datum of 1988 0.1 meters Explicit elevation coordinate included with horizontal coordinates BS_SGP_2024_ERT_Points.shp Shapefile containing coordinates of electrodes for all lines U.S. Geological Survey FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Shape type. Line Line name U.S. Geological Survey LW_Creek Lower Creek U.S. Geological Survey UP_Creek Upper Creek U.S. Geological Survey UP_Land Upper Land U.S. Geological Survey Elec Electrode Number U.S. Geological Survey 1 63 Dist Nominal electrode distance along line U.S. Geological Survey 0 434 meters 1 Easting Easting coordinate, NAD83 UTM Zone 11N U.S. Geological Survey 500918.41 501611.06 meters 0.01 Northing Northing coordinate, NAD83 UTM Zone 11N U.S. Geological Survey 3756514.6 3757744.7 meters 0.01 Elevation Ground surface elevation, NAVD88 U.S. Geological Survey 776.7 813.4 meters 0.1 Data are organized by file type in .zip compressed file folders. In each .zip file, there are equivalent files for each survey line, indicated in the file name prefix: BS_SGP_UPLAND_ERT_XXXX.file – data related to the upper survey line outside the channel BS_SGP_LWCREEK_ERT_XXXX.file – data related to the lower survey line inside the channel BS_SGP_UPCREEK_ERT_XXXX.file – data related to the upper survey line inside the channel Each electrical resistivity tomography survey line consists of: - Raw data file in .stg format - Electrode elevation file in .trn format - Processed data in .stg format and a .png image of the preliminary processed data - Modeled outputs in .csv file format Data dictionaries describing column information for each file type is explained in their respective zip files and are indicated with “XXXX_DataDictionary.csv”. File types are described in greater detail below. Raw_Data.zip – raw data files collected in the field. Data dictionary file – ‘BS_SGP_2024_ERT_RawData_DataDictionary.csv' Raw data files are in the .stg format. The .stg files are best used with Advanced Geosciences EarthImager(TM) 2D (Advanced Geosciences, Inc., Austin, Texas) but can be opened using basic text editors. The .stg files have a four-line header preceding the data and contain 27 columns. The first four columns are populated with acquisition data regarding the record number, user, acquisition date and time. Columns five through eight are calculations for resistance in Ohms and percent error, measured injected current in milliAmps, and calculated apparent resistivity. The ninth column is the command file name. Columns ten through twenty-one are relative coordinates in the x, y, z directions for the A-electrodes, B-electrodes, M, electrodes, and N-electrodes in meters. The final six columns are the command file execution line number, transmitter voltage in volts, number of measurement cycles, measurement time duration, receiver gain, and instrument receiver channel number, respectively. Raw data files are named by site and have ‘_raw’ appended to the file name. Additionally, '_SG' is further appended to the file name for the strong-gradient surveys, '_DD' is appended to the file name for dipole-dipole surveys, and '_comb' is appended to the file names for the concatenated data containing both strong-gradient and dipole-dipole surveys. Terrain_Files.zip – data related to terrain files. Data dictionary file – BS_SGP_2024_ERT_Terrain_File_DataDictionary.csv’ Terrain data files are in the .trn format. Each elevation .trn file consists of a three-line header, and two columns of data. The first column is the electrode distance along the survey in meters, the second column is the estimated elevation of each electrode location. The format of each .trn file is identical. Data files are named by site and have '_TRN' appended to the file name. Processed_Data.zip – processed data files. Data dictionary file – 'BS_SGP_2024_ERT_ProcessedData_DataDictionary.csv' Processed data files have an identical .stg format. The .stg files are best used with Advanced Geosciences EarthImager(TM) 2D (Advanced Geosciences, Inc., Austin, Texas) but can be opened using basic text editors. The .stg files have a four-line header preceding the data and contain 21 columns total. The first four columns are populated with acquisition data regarding the record number, user, acquisition date and time respectively. Columns five through eight are calculations for resistance in Ohms and percent error, measured injected current in milliAmps, and calculated apparent resistivity. The ninth column is the command file name. Columns ten through twenty-one are relative coordinates in the x, y, z directions for the A-electrodes, B-electrodes, M, electrodes, and N-electrodes in meters. The processed data files are named by site and have '_proc' appended to the file name. In addition to the processed .stg files, each zipped folder contains an image of the preliminary processed data in .png format with ‘EI_output_Hoogenboom2025_CC0’ appended to the file name. Advanced Geosciences EarthImager(TM) 2D (Advanced Geosciences, Inc., Austin, Texas) (TM) software applies a color scale to the data which describes larger values in red as being more resistive while lower values in blue are more conductive. Model_Data.zip – modeled data files. Data dictionary file – 'BS_SGP_2024_ERT_Models_DataDictionary.csv' The modeled data files are in the .csv format. Each file consists of a single header line and six columns of data. The first column is the electrode distance along the survey in meters, columns two and three are coordinates in NAD83 in meters, the fourth column is the estimated elevation of each electrode location in meters. The fifth column is populated by modeled resistivity values in Ohm-meters, and the sixth column describes the unitless sensitivity mask, which is a proxy for uncertainty. The modeled data files are named by site and have '_model' appended to the file name. Shapefile.zip Survey locations are included in the 'BS_SGP_2024_ERT_Points' shapefile. Explanatory information for the shapefile is provided in the Entity and Attribute section of the metadata file. Data files and data dictionaries associated with the ERT data are available at: https://doi.org/10.5066/P16PH76Q ScienceBase U.S. Geological Survey mailing and physical address

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase_datarelease@usgs.gov https://www.sciencebase.gov/catalog/item/680ed046d4be024491bea15e Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. CSV, shapefile https://doi.org/10.5066/P16PH76Q None None 20251219 Bennett E. Hoogenboom U.S. Geological Survey, California Water Science Center Geophysicist mailing and physical address

6000 J Street, Placer Hall, CAWSC

Sacramento CA 95819 United States 916-278-3000 bhoogenboom@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998