Sydney M. Welch James R. Degnan Neil C. Terry Eric A. White Leah M. Santangelo 20250911 tabular digital data Science Base U.S Geological Survey https://doi.org/10.5066/P17MB5MH In 2024 the U.S. Geological Survey (USGS), in cooperation with the Air Force Civil Engineer Center (AFCEC), conducted geophysical surveys at Hanscom Air Force Base, Hanscom Field, and surrounding areas in Massachusetts. Methods used included frequency-domain electromagnetic induction (EMI), ground-penetrating radar (GPR), horizontal-to-vertical spectral ratio (HVSR) passive seismic, electrical resistivity tomography (ERT), and transient electromagnetic induction (TEM). These data can be used to help identity aquifer boundaries, and properties. Data collection locations were determined by considering hydrologic information from previously published investigations. Specific information on the geophysical methods used and details about each instrument are provided in the Supplemental Information section of this data release. The purpose of this data release is to present surface geophysical data collected at and adjacent to Hanscom Air Force Base and Hanscom Field. These data can support the characterization of subsurface conditions, including the determination of aquifer properties. The following geophysical methods and instruments were used: (1) EMI: a DUALEM-421 (serial number 335, DualEM, Inc.) was used. This instrument uses a single frequency at 9 kHz with various transmitter-receiver coil spacings and orientations. Larger coil spacings enable deeper subsurface measurements (at lower resolution), while smaller spacings offer higher-resolution measurements at shallower depths. (2) GPR: GPR surveys were conducted using a MALA GX controller (ID:227603071) running software version 15.2.269.39, paired with GroundExplorer 80 MHz, and 450 MHz shielded antennas (ID:1513002). This system uses an antenna with a fixed transmitter-receiver offset contained within a tow-body to collect common offset data along profile lines. The GPR antenna transmits electromagnetic pulses into the subsurface, and the system records the amplitude and travel time of reflections (Keary and Brooks, 1991) from soil interfaces with contrasting electromagnetic properties. (3) HVSR: A Tromino TEP-3C three-component seismometer (MoHo s.r.l.) was used to record directional ambient seismic noise. HVSR analysis provides an estimate of the resonance frequency (f0) of unconsolidated sediments over bedrock, where a substantial contrast in shear-wave acoustic impedance exists (> 2:1). Spectral ratio analysis of the horizontal, and vertical components of the seismic data is used to determine f0. Overburden thickness can be related to f0 with thicker overburden related to lower frequencies, and thinner overburden related to higher frequencies. (4) ERT: ERT measurements were conducted using a Supersting R8 resistivity meter, and a 56-electrode switchbox (S/N: SS1004079, Advanced Geosciences, Inc.) resistivity meter, and a 56-electrode switchbox (S/N: SS1004079, Advanced Geosciences, Inc.) with 3-meter interelectrode (A) spacing cables. In the ERT surveys, electrical current is injected through two current electrodes, and voltage is measured across multiple pairs of potential electrodes. Apparent resistively is calculated based on the known current, and the measured voltages. (5) TEM: A sTEM-profiler (S/N: V009A240013, TEM company of Denmark) was used to conduct TEM surveys, which provide resistivity soundings of the subsurface. Electrical current is cycled through a wire placed on the land surface in a transmitter loop (Tx), producing a static magnetic field. When the current is abruptly terminated, it induces a secondary current in the subsurface. The decay rate of these induced currents is controlled by the resistivity of subsurface materials. Data provided in this data release are: (1) raw GPR profile data in the *.rd3, and *.rd7 formats, (2) raw DUALEM-421 data in comma-separated values (*.csv) files, (3) processed DUALEM files with ‘_combined’ in the filename, and (4) inverted DUALEM profiles with ‘_inv’ in the filename. (5) raw HVSR data in the *.saf, and *.trc files. (6) Raw ERT data in *.stg format. (7) inverted ERT data with ‘Inverted_ERT’ in the filename. (8) raw TEM data in *.usf files. Any use of trade, firm, or product names is for descriptive purposes only, and does not imply endorsement by the U.S. Government. 20240729 20240927 ground condition Complete None planned -71.32427 -71.23878 42.49742 42.43815 ISO 19115 Topic Category inlandWaters environment Thesaurus Horizontal-to-Vertical Spectral Ratio (HVSR) Seismic Electromagnetic Induction Passive Seismic Surface Geology Bedrock Transient Electromagnetic Induction (TEM) USGS Thesaurus Geophysics ground penetrating radar Resistivity Groundwater Hydrogeology USGS Metadata Identifier USGS:671911a1d34e23541cc16dec Place Hanscom Air Force Base Massachusetts None. Please see 'Distribution Info' for details. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Although these data have been processed successfully on a computer system at 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. The USGS or the U.S. Government shall not be held liable for improper or incorrect use of the data described and/or contained herein. Sydney M Welch USGS - Northeast Region Physical Scientist mailing and physical

New England WSC NH Office,331 Commerce Way

Pembroke NH 03275-3718 603-226-7800 smwelch@usgs.gov Air Force Civil Engineer Center (AFCEC) for funding, Ashley Grengs, and Daphne Smith for field support. No formal attribute accuracy tests were conducted; however, tools were calibrated by the manufacturer. Results were compared to published results from this area and to other data sets collected at the site. 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 and the associated extended abstract for additional details. No formal positional accuracy tests were conducted. No formal vertical accuracy tests were conducted. MALA 2024 publication https://wwwguidelinegeoc.cdn.triggerfish.cloud/uploads/2020/06/MALA-Ground-Explorer-GX-Antennas-WiFi-Wire-October-2024.pdf Digital and/or Hardcopy 20240729 20240929 ground condition MALA, 2024 GPR manual Beres, M. Haeni, F.P. 199105 publication Groundwater vol. 29, issue 3 ppg. 375-386 https://doi.org/10.1111/j.1745-6584.1991.tb00528.x Digital and/or Hardcopy 20240729 20240927 ground condition Beres and Haeni 1991 Referenced in abstract and GPR processing step Hoogenboom, B.E. Preston, T.M. Smith, B.D. Moulton, C.W. Ball, L.B. 20201023 dataset https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/p9ny3uju Digital and/or Hardcopy 20240729 20240927 ground condition Hoogenboom Electromagnetic data collection with DUALEM processing step. DUALEM 2024 publication Accessed October 22nd, 2024 https://dualem.com/documents/dualem-manual/ Digital and/or Hardcopy 20240729 20240927 ground condition DUAL Manual Manual for DUALEM Koller, M.G. Guillier, J.L. Duval, A.M. Atakan, K. Lacave, C. Lacave, P.Y. 20040806 publication https://www.researchgate.net/profile/Jean-Luc-Chatelain/publication/235984865_PRACTICAL_USER_GUIDELINES_AND_SOFTWARE_FOR_THE_IMPLEMENTATION_OF_THE_HV_RATIO_TECHNIQUE_MEASURING_CONDITIONS_PROCESSING_METHOD_AND_RESULTS_INTERPRETATION/links/0deec515320961cb70000000/PRACTICAL-USER-GUIDELINES-AND-SOFTWARE-FOR-THE-IMPLEMENTATION-OF-THE-H-V-RATIO-TECHNIQUE-MEASURING-CONDITIONS-PROCESSING-METHOD-AND-RESULTS-INTERPRETATION.pdf?_tp=eyJjb250ZXh0Ijp7ImZpcnN0UGFnZSI6InB1YmxpY2F0aW9uIiwicGFnZSI6InB1YmxpY2F0aW9uIn19 Digital and/or Hardcopy 20240916 20240920 ground condition Koller and others 2024 Reference in HVSR processing step. Blanchy, G Saneiyan, S Boyd, J McLachlan, P 2020 publication https://doi.org/10.1016/j.cageo.2020.104423 Digital and/or Hardcopy 20240906 ground condition Blanchy and others ERT processing. Kearey, P Brooks, M 1991 2nd publication Digital and/or Hardcopy 2024 ground condition Keary and Brooks, 1991 Abstract EMI collection (Process Step 1) Electromagnetic data was collected using the DUALEM-421 sensor, a multi-coil spacing frequency-domain electromagnetic induction sensor with a single transmitter (Tx) coil operating at 9kHz, and six receiver coils with transmitter-receiver separations of 1, 2, and 4 meters (m) in horizontal co-planar (HCP), and perpendicular (PRP) coil orientations to measure conductivity at different depths. The DUALEM was connected to a differential global positioning system (DGPS, Emlid Reach RS2+), which at some sites was set up with a base station (also an Emlid Reach RS2+) to provide real-time kinematic (RTK) corrections. The DUALEM at each site was on a cart 0.305 m above the land surface and towed with a vehicle or hand-towed at walking speed. Sites: Airfield_SWtriangle: The site is a triangular area of grass-covered land to the southwest of Runway 5, bordered by taxiways within the Hanscom Field. The DUALEM-421 was towed on the cart by a vehicle, with GPR equipment collecting concurrent data (process step 2) 16 m from the bumper. Airfield_Srunway29: The site is a rectangular area of grass covered land south of Runway 29 on the east site of the Hanscom Field. The DUALEM-421 was on the cart and positioned 16 m from the vehicle's bumper. The DUALEM-421 was towed along with the GPR equipment, which collected concurrent data (process step 2). Airfield_Nrunway29: The site is a grass area north of Runway 29 on the east side of Hanscom Field. The DUALEM-421 was towed with GPR equipment collecting concurrent data (process step 2) on the cart with a vehicle, 16 m from the bumper. FamCamp_Woods: The site is a wooded area northeast of Hanscom Field. The DUALEM-421 was towed by hand on the cart at walking speed along trails in the woods. SouthRoad_Soccerfield: This site is a soccer field adjacent to the Hartwell Town Forest. The DUALEM-421 was towed on the cart, 4 m behind the tow vehicle. At this site, the Global Positioning System (GPS) was attached to the DUALEM-421 to provide RTK corrections. OU2-IRPSite4_Landfill: This site is a capped landfill, currently used as a softball field, southwest of Hanscom Field. The DUALEM-421 was towed on the cart along with GPR equipment collecting concurrent data (process step 2) 8.6 m behind the tow vehicle. At this site, the GPS was attached to the DUALEM-421 to provide RTK corrections. HartwellTownForest: This site located within the Hartwell Town Forest located northeast of Hanscom Field. The DUALEM-421 was towed by hand on the cart at walking speed. 20240729 GPR collection (Process Step 2) GPR surveys primarily used a transmitting and receiving 80 Megahertz (MHz) antenna and, in some cases, a higher resolution 450 MHz antenna (MALA, 2024). Radio wave pulses centered at these frequencies were transmitted into the ground to image the subsurface. The radar-wave propagation is affected by differences in electromagnetic properties of the subsurface materials including dielectric permittivity, electrical conductivity, and magnetic susceptibility caused by differences in lithology, water conductance, and sediment type (Keary and Brooks, 1991). The penetration of GPR signals is limited where the radar-wave reflection is attenuated by electrically conductive subsurface materials or scattered from discrete objects too small to generate a coherent geometric reflection, such as cobbles, and boulders. Radar-wave penetration, and velocities will vary with study area properties. Published velocity estimates (Beres and Haeni, 1991), and velocity measurements from MALA software (MALA, 2024) were used to calculate the depth from reflected radar-wave travel time. A differential global positioning system (DGPS, Emlid Reach RS2+) was used for georeferencing at five out seven of the sites (Airfield_Nrunway29, Airfield_Srunway29, Airfield_SWtriangle, FamCamp_Woods, HartwellTownForest). Real-time kinematic (RTK) GPS data was used at the SouthRoad_Soccerfield site, and the internal GPS of the GPR antenna was used at site OU2-IRPSite4_Landfill. GPR was collected using an odometer survey wheel to precisely measure distance. Display gain was adjusted by multiplying data by a constant to increase or decrease signal amplitude to provide an improved image. Sites: Airfield_SWtriangle: This site was a triangle of grass-covered land to the southwest of Runway 5 and bordered by taxiways on the Hanscom Field. The 80 MHz antenna was towed 5m behind the tow vehicle concurrently with the DUALEM-421 (0.305 m behind the tow vehicle). Airfield_Srunway29: This site was a rectangle of grass-covered land south of Runway 29 on the eastern end of the Hansom Field. The 80 MHz antenna GPR was towed concurrently with the DUALEM-421 (0.305 m behind the tow vehicle). Airfield_Nrunway29: This site was grass covered land north of Runway 29 on the eastern end bordering FamCamp on Hanscom Field. The 80 MHz antenna GPR was towed concurrently with the DUALEM-421 (0.305 m behind the tow vehicle). FamCamp_Woods: This site was in the woods of FamCamp northeast of Hanscom Field. The 80 MHz antenna GPR was towed by hand on a cart at walking speed along trails in the woods at FamCamp. SouthRoad_Soccerfield: This site was a town soccer field on the north side of South Road adjacent to the Hartwell Town Forest. The 80 MHz, and 450 MHz antenna were towed up, and down the soccer field from southeast to northwest. The 80 MHz GPR was dragged at a steady walking pace, and the 450 MHz was towed 4m behind a vehicle. OU2-IRPSite4_Landfill: This site was a landfill southwest of Hanscom Field on the west side of Virginia Road. The 80 MHz antenna GPR was towed on a cart 8.6 m behind the tow vehicle concurrently with the DUALEM-421 (process step 1). HartwellTownForest: This site was at Hartwell Town Forest located northeast of Hanscom Field. The 80 MHz antenna, and 450 MHz antenna GPR were towed at walking speed along hiking trails in the Hartwell Town Forest. 20240729 HVSR collection (Process Step 3) Three Model TEP-3C Tromino seismometers (available from MoHo) were used independently for the horizontal-to-vertical spectral ratio (HVSR) measurements. The general procedure for collecting the HVSR data is described by the following steps (Koller and others, 2004): (1) select a measurement site free of infrastructure, and soft debris. (2) orient seismometer to magnetic north, and firmly couple with the earth by pressing the spikes on the bottom of the unit into the ground or placing it on a coupling plate. (3) level the seismometer using the spirit level on the top of the unit; and (4) record data for 20 minutes per site. Data files in a proprietary format with a .trc extension were downloaded from the Tromino seismometers using Grilla Rel. 9.7.2 (beta) software. Grilla software was used to export the .trc files as ascii format files with a .saf file extension. Sites: Airfield_Nrunway23: This site was a grass covered area north of Runway 23 on the northeast end of the runway. Airfield_Nrunway29: This site was a grass covered area north of Runway 29 on the eastern end bordering FamCamp on Hanscom Field. Airfield_SErunway5: This site was a grass covered area east of Runway 5 on the southern end of the runway. Airfield_SWtriangle: This site was a triangle of grass covered land to the southwest of Runway 5 and bordered by taxiways on Hanscom Field. FamCamp_Woods: This site was in the woods of FamCamp northeast of Hanscom Field. FamCamp_Road: This site was at FamCamp northeast of Hanscom Field. 20240916 TEM-profiling (Process Step 4) The TEM-profiling system is relatively small compared to other TEM equipment, is portable, and can be hand-carried by two or three people. TEM-profiling uses an offset-sounding configuration with a 3 m square transmitter, and 3 m square receiver. The transmitter-receiver offset was 10 m. TEM data were collected using two transmitter moments consisting of low, and high moments. The low-moment is used for investigation of shallow earth materials, and energizes the transmitter loop using 1 amp, and data are received at six time gates. The high-moment is used to investigate deeper earth materials, and uses 10 amps of electrical current during the measurement, and were received at 22 time gates. Measurements from both moments were combined, cleaned to remove coupled or noisy data, and inverted as individual one-dimensional soundings. Measurements lasting 2 minutes were taken at fixed locations along five profiles at five sites on, and around Hanscom Air Force Base. Sites: Airfield_SWtriangle: This site was a triangle of grass covered land to the southwest of Runway 5 and bordered by taxiways on Hanscom Field. The TEM profile containing the least amount of noise from infrastructure was collected in the southwest quadrant. At the southwest triangle of the airfield, a TEM profile was collected along DUALEM-421, and GPR profiles. The TEM profile was terminated short due to significant noise increasing observed in the data from nearby infrastructure. Airfield_Srunway29: This site was a rectangle shape of grass covered land south of the of Runway 29 on the east end on Hanscom Field. Airfield_Nrunway29: This site was a grass covered land area north of Runway 29 on the eastern end bordering FamCamp on Hanscom Field. SouthRoad_Soccerfield: This site is a town soccer field on the north side of South Road adjacent to the Hartwell Town Forest. HartwellTownForest: This site is at the Hartwell Town Forest located northeast of Hanscom Field. 20240924 Eric White USGS Hydrologist mailing

Unit-5015

Storrs-Mansfield Connecticut 06269 United States 860-487-7402 eawhite@usgs.gov ERT Collection (Process Step 5) 1. Using start, and end electrode positions recorded with a handheld GPS in the field, electrode positions were interpolated using R’s (version R4.4.0) “approxfun” function (R package version 3.6-26) to relate distance along the line to geographic positions, and thus provide a geographic coordinate for each electrode along the line (contained in “ERT_coordinates.csv”). 2. Measurements from both Wenner-Schlumberger, and Dipole-Dipole surveys were combined into a single file. 3. Data inversion used the R2 code (Andrew Binley, Lancaster University, v. 4.02), and graphical user interface ResIPy (Blanchy and others, 2020, v. 3.5.4). The following steps were carried out: -Imported data using the “Sting” file format. -Filtered measurements with apparent resistivity less than 0. -Established a mesh with a fine/coarse boundary depth of 30 m. -Assigned errors as 0.05x + 0.1 Ohms, where x is the data value in Ohms. -Ran the inversion. -The inversion converged smoothly within 3 iterations. -Results were output in standard R2 formats. 4. R2 outputs were converted in file "inverted_ERT.csv" – see data dictionary for details. Site: Airfield_Nrunway29: This site is a grass covered land area north of Runway 29 on the east end bordering FamCamp on Hanscom Field. 20240926 Neil C Terry USGS - Northeast Region Research Hydrologist mailing and physical

NYWSC - Troy District Office

Troy NY 12180 860-487-7402 nterry@usgs.gov EMI Processing (Process Step 6) 1. Coordinate corrections were performed for certain airfield SW triangle data files. Summary: Positions were corrected for files with errant GPS The GPS data stream was errant for files DUALEM-148853.csv, DUALEM-148927.csv, DUALEM-149211.csv, DUALEM-149694.csv, DUALEM-150007.csv, and DUALEM-151035.csv. To provide coordinates for these files, coordinates, and timestamps from GPR GPS data (collected simultaneously with the DUALEM) were compared from previous lines in R to establish temporal offset between instrument internal clocks – the DUALEM clock was found to be approximately 185 seconds ahead of the GPR. Corrected coordinates to the DUALEM files were thus supplied as the GPR coordinates from 185 seconds prior to the DUALEM file timestamps. 2. Combination of raw file. Multiple raw data files from individual sites were combined into a single file and given filenames like SITENAME_DUALEM-combined.csv. A forward slash (/) was added to the first row of these files so that the inversion program could recognize this line as a header. 3. Assign elevation. Summary: DEM elevations were assigned to each data point. Details: Elevation is not explicitly needed for data inversion but was added for ease of plotting, and interpretation later. Files were given elevations based on best-available resolution digital elevation data with full site coverage from the USGS National Elevation Dataset, downloaded October 2024: USGS_1M_19_x30y471_MA_CentralEastern_2021_B21.tif USGS_1M_19_x31y471_MA_CentralEastern_2021_B21.tif Elevation values were extracted, and appended to each data point in the files using the "extract" function in the R raster package. These data can be found in the "dem_elevation_m" column of CSV files. 4. Application of constant shift to soccer field, and landfill data. Summary: corrected 1 m coil apparent electrical conductivity data for constant offset. Details: Attaching the instrument battery pack directly to the bottom of the instrument caused an apparent constant shift in the 1 m coil data values (H1mS_m, P1mS_m) for earlier surveys (soccer filed, and landfill). These 1-m data values were thus shifted using the 5% quantile value (used instead of minimum, given local spikes) in the raw data for each site such that minimum data values were approximately zero. The corrections added were as follows: OU2-IRPSite4_Landfill site: H1mS_m: -206.2 millisiemens/meter P1mS_m: +124.2 millisiemens/meter SouthRoad_Soccerfield site: H1mS_m: -209.2 millisiemens/meter P1mS_m: 118.7 millisiemens/meter 5. Data import for inversion (creation of depth versus electrical conductivity profiles) of electromagnetic data in Aarhus Workbench. Summary: processed data were imported into Aarhus Workbench, and assigned error models. Details: Aarhus Workbench (Version 2024.1.1.0) was used for EMI data inversion. Data were imported using the GCM (ground conductivity meter) module. This includes inputs such as the coil configurations, height of sensor, and column mapping to inversion-relevant data (i.e., position, and apparent conductivity data data). Sensor height was set to 0.305 meters as measured in the field. Upon import, an estimate of the data errors for each coil configuration is also needed. These errors, in part, determine the criteria used to gauge when inversion models have converged. Errors are assigned using a linear model, with an intercept (absolute error), and slope (offset) which are applied to data values. Error assignments were carried out based on experience, stationary surveys (i.e., standard deviation of data values when the sensor is held still), and repeatability of data along repeat transects. For the DUALEM-421, the error model was 1.1x + 0.1 millisiemens/meter (where x is the data value in millisiemens/meter). 6. Resampling/smoothing. Summary: Imported data were resampled, and smoothed. Details: Aarhus Workbench requires a "processing" step prior to inversion, wherein raw data are resampled to a regular interval, and optionally smoothed using moving averaging windows. DUALEM sensor data were resampled to 1 m sounding spacing and used 3 m moving window averaging (smoothing) for all coil configurations. 7. LCI inversion, and export of results. Summary: Data were inverted using smoothness constraints, and then results were exported. Details: Aarhus Workbench can use a smooth, laterally constrained inversion (LCI) to invert for depth-EC along 2D profiles. This type of inversion encourages individual 1D depth-EC profiles to be similar to profiles immediately before, and after. It also encourages the 1D depth-EC (electrical conductivity) profiles to be "smooth" in the vertical. These steps are generally required to prevent large, and unrealistic EC variations in the vertical, and lateral directions caused by issues of model equivalence (i.e., multiple, and significantly different 1D depth EC profiles can fit the data). The LCI + smooth inversion approach effectively improves the consistency of final results and is a standard approach for inverting EMI data. Several sub-options within the inversion are available, including setting the number, and depth of model layers, tuning the smoothness constraints, and defining a starting model. For these data, a laterally constrained smooth inversion with default regularization parameters, and 20 fixed log-spaced layers down to 20 m depth was used. Inversions were performed until convergence, and the resulting inverted models/data were exported from Workbench to *_inv.xyz/*_dat.xyz files respectively. Please see "DataDictionary_EMI.csv" for descriptions of the output files. 20241104 Neil C Terry USGS - Northeast Region Research Hydrologist mailing and physical

NYWSC - Troy District Office

Troy NY 12180 860-487-7402 nterry@usgs.gov Hanscom_HVSR.csv Comma Separated Values (CSV) file containing data. Producer Defined Site Site of HVSR measurement. Producer Defined Airfield_Nrunway23 HVSR site Producer defined Airfield_Nrunway29 HVSR site Producer defined Airfield_SErunway5 HVSR site Producer defined Airfield_SWtriangle HVSR site Producer defined FamCamp_Woods HVSR site Producer defined FamCamp_Road HVSR site Producer defined Sensor ID of the sensor used to collect data. Producer Defined 513 Sensor ID Producer defined 133 Sensor ID Producer defined Partition The number of the data partition in the sensor used to collect data. Producer Defined 13 34 Latitude Latitude coordinate of the sensor. Producer Defined 42.46485629 42.47542956 Decimal Degrees Longitude Longitude coordinate of the sensor. Producer Defined -71.29884314 -71.27600279 Decimal Degrees Elevation Elevation of the sensor in feet. Producer Defined << empty cell >> No data recorded. Producer defined 9.706 178.52 Feet Date Date of the data collection. Producer Defined 9/17/2024 9/20/2024 mm/dd/yyyy Time Time of the data collection in eastern standard time. Producer Defined 10:05 9:44 hh:mm Geophysical data is contained in data folders. Data is organized by geophysical instrument and site. Hanscom_EMI_Data folder contains: Raw EMI data (DUALEM-XXXXXX.csv) at each site. Processed EMI data ('_combined' in file name) at each site. Inverted EMI data ('inv' in the filename) at each site Data Dictionary for raw EMI data (DataDictionary_EMI_raw_data.csv) Data Dictionary for processed and inversion EMI data (DataDictionary_EMI_Inversion_Processed_Result.csv) Hanscom_GPR_Data folder contains: Raw GPR data (DAT_xxx) containing COR, MRK, RAD, RD3, RD7 and SRD files for each site. Data Dictionary for GPR data (DataDictionary_GPR) Hanscom_HVSR_Data folder contains: Raw HVSR data (SAF and TRC files) for each site. HVSR measurement location (Hanscom_HVSR.csv) Hanscom_ERT_Data folder contains: Raw ERT data (Windows Command Script, CRS file, STG file and Text file) for site. Data Dictionary for ERT (DataDictionary_ERT.csv) Coordinates for ERT (ERT_coordinates) Inverted ERT data (Inverted_ERT.csv) Hanscom_TEM_Data folder contains: Raw TEM data (USF file) for each site. See geophysics data at https://doi.org/10.5066/P17MB5MH U.S. Geological Survey GS ScienceBase mailing address

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov 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. Digital Data https://doi.org/10.5066/P17MB5MH None 20250911 Sydney M Welch USGS - Northeast Region Physical Scientist mailing and physical

New England WSC NH Office,331 Commerce Way

Pembroke NH 03275-3718 603-226-7800 smwelch@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998