Geophysical Survey.pdf

Final Geophysical Survey Report

Indoor Target Flip Facility Holloman AFB, NM

Jacobs Contract No. W912PP-21-D-0003

Prepared for:

9191 Jamaica Street Englewood, CO 80112

Prepared by:

222 Valley Creek Blvd.

Suite 140

Exton, PA 19341

March 2023

Indoor Target Flip Facility

Holloman AFB, NM

TerranearPMC, LLC i March 2023 Contract No. W912PP-21-D-0003 Final

TABLE OF CONTENTS

Page No.

1.0 INTRODUCTION

1.1 SCOPE OF WORK

1.2 SITE LOCATION AND DESCRIPTION

2.0 EQUIPMENT

3.0 METHODOLOGY

3.1 DGM SURVEY ACTIVITIES

3.2 EM61-MK2 DGM DATA PROCESSING

3.3 EM31-MK2 DGM DATA PROCESSING

3.4 QUALITY CONTROL

4.0 RESULTS

4.1 SUMMARY OF WORK PERFORMED

4.2 MOBILIZATION AND SITE SETUP

4.3 DGM SURVEY ACTIVITIES

4.4 DATA INTERPRETATION

5.0 DGM INSTRUMENTS AND POSITIONSING SYSTEMS QC RESULTS

6.0 CONCLUSIONS AND LIMITATIONS

7.0 REFERENCES

Holloman AFB, NM

TABLE OF CONTENTS (CONTINUED)

TerranearPMC, LLC ii March 2023 Contract No. W912PP-21-D-0003 Final

LIST OF FIGURES

Figure 1 General Location of White Sands Missile Range, New Mexico Figure 2 Site Location Map

LIST OF ATTACHMENTS

Attachment 1 Tabloid-size Mosaic Plates(s) Showing DGM Results Plate 1 EM61-MK2 Channel 2 Response Plate 2 EM31-MK2 Inphase Response Plate 3 EM31-MK2 Conductivity Response

Attachment 2 Electronic Deliverables (Includes all Data, Deliverables)

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TerranearPMC, LLC iii March 2023 Contract No. W912PP-21-D-0003 Final

LIST OF ACRONYMS

ac acre/acres AFB Air Force Base DGM Digital Geophysical Mapping ft foot/feet ISO Industry Standard Object Jacobs Jacobs Engineering Group Inc.

mi mile/miles MQO Measurement Quality Objective mS/m milliSiemens per meter mV millivolts NAD83 North American Datum 1983 NE Northeast ppt parts per thousand QC Quality Control RTK-GNSS Real-time Kinematic-Global Navigation Satellite System SW Southwest TDEM Time Domain Electromagnetic TPMC TerranearPMC WSMR White Sands Missile Range

Holloman AFB, NM

TerranearPMC, LLC 1 March 2023 Contract No W912PP-21-D-0003 Final

1.0 INTRODUCTION

TerranearPMC (TPMC) was contracted by Jacobs Engineering Group Inc. (Jacobs) to conduct a geophysical survey at the proposed site of the Indoor Target Flip Facility and associated parking area/site work. The site is located at White Sands Missile Range (WSMR) adjacent to Holloman Airforce Base (AFB) in Alamogordo, New Mexico. The geophysical survey and follow-up investigations by Jacobs are being conducted in support of the United States Army Corps of Engineers, Albuquerque District, Contract W912PP-21-D-0003.

1.1 SCOPE OF WORK

The scope of work consisted of EM61-MK2 and EM31-MK2 Digital Geophysical Mapping (DGM) surveys conducted at the site at WSMR. Survey coverage with both the EM61-MK2 and EM31- MK2 was planned for the entire site, however EM61-MK2 survey was prioritized for the 9 planned borehole locations to complete the project within the planned schedule and fulfill the data requirements. The objective of the geophysical survey was to delineate the lateral extent of potentially disturbed soils and subsurface obstructions including, but not limited to, metallic and non-metallic wastes, former building foundations, and utilities. The survey required sufficient sensitivity to detect any buried utilities or debris up to a maximum of 6 feet (ft) in depth or the full depth of expected excavation required at the site.

1.2 SITE LOCATION AND DESCRIPTION

The project site was in a remote area of WSMR located ~45 miles (mi) northwest of Alamogordo, New Mexico as shown in Figure 1. The geophysical survey area encompassed approximately 16.4 acres (ac) and is depicted in Figure 2.

Minimal information exists on the site history and site conditions. It was not known whether buried debris or obstructions are present within the proposed construction footprint. The types, composition, depths, and extent of wastes potentially underlying the site are also unknown. As a result, the geophysical survey was conducted primarily as a precautionary measure, the results of which will assist in minimizing cost and schedule impacts to the facility construction.

There was at least one known fiber optic underground utility present at the site that was marked prior to the start of the geophysical survey. To the north of the roadway, the site was thickly vegetated along an escarpment and was intersected by a drainage channel. Powerlines were located ~45 ft south of the road and ran parallel to the roadway for nearly the entire length of the survey area. To the south of the roadway, the site had a large, flat area (~3.4 ac) partially cleared of vegetation. Four large mounds of dirt and cleared debris were present along the eastern boundary of the cleared area. The northern and southern boundaries of the site were gradually sloped towards two channels, while the southeastern area was intersected by undulating to steep terrain due to several arroyos. The uncleared portions of the site were highly vegetated with mesquite ranging from ~2 to 10 ft tall. Some small surface metals/debris were present. Their locations are presented in Attachment 2.

The site was conducive to the use of a Real-time Kinematic-Global Navigation Satellite System (RTK-GNSS). The nearest known benchmark was located ~1 mi away at Pit 3 (coordinates were provided by WSMR staff), and the field team used this benchmark to establish a control point (TPMC-01) at the site to extend the range of RTK-GNSS equipment throughout the survey area. Coordinates for Pit 3 and TPMC-01 are also presented in Attachment 2.

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TerranearPMC, LLC 2 March 2023 Contract No W912PP-21-D-0003 Final

Because the project site was in a secure area, photographs by the field team were not permitted. Several site photographs were taken on March 1, 2023 by a cleared security escort and are included in the Attachment 2 photo log.

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TerranearPMC, LLC 5 March 2023 Contract No. W912PP-21-D-0003 Final

2.0 EQUIPMENT

The DGM sensor and positioning system utilized are described below:

Geonics EM61-MK2

The EM61-MK2 is a high-sensitive time domain electromagnetic (TDEM) system that detects both ferrous (i.e., iron) and non-ferrous (e.g., aluminum, copper, brass, etc.) metals. The EM61- MK2 generates an EM pulse in the bottom transmitter coil causing eddy currents to flow in both the ground and within possible buried metallic objects. When the electromagnetic pulse is terminated, the eddy currents decay which produces a changing electromagnetic field, also referred to as a secondary electromagnetic field. The eddy currents decay more slowly in metallic objects than in the ground, creating a higher, measurable electromagnetic field. This is the signal recorded by the EM61-MK2 system (a low-level signal is recorded when no metal is present). This electromagnetic signal is generally at the maximum level when the receiver coils are located directly over a metallic object. The EM61-MK2 system records this signal at three-or four-time intervals, referred to as time gates or channels, after the transmitter is turned off.

Four-time gates/channels (220, 360, 660, and 1,200 microseconds) can be recorded (measured in millivolts [mV]). Compared to other geophysical systems, the EM61-MK2 is effective in detection of metal directly below the survey measurement and less sensitive to lateral interferences. Therefore, structures such as fences, buildings, and power lines not directly adjacent to the EM61-MK2 survey transect will produce significantly less response than for other metal detectors. The primary factors that affect the ability of the TDEM method to detect metallic objects include size, mass, orientation, and distance of the metallic object from the sensors. Sufficient contrast between the metallic objects and surrounding materials must also exist for the metallic object to be identified in the TDEM data.

The EM61-MK2 is designed so that it is possible not only to separate anomalies laterally, but also, under most conditions, to distinguish deeper targets from shallow ones. In addition, the unique two-receiver coil system allows suppression of near surface targets that may mask response from deeper, more important ones using the differential mode of operation. This feature is very useful when the purpose of the survey is to locate deeper targets, like underground storage tanks or drums, in presence of shallow near surface metallic objects (manhole cover or metal scrap). Negative values on the differential channel map are often associated with the metallic objects located above the surface, assuming the depth coefficient of one is used (normal practice).

Geonics EM31-MK2

The Geonics EM31-MK2 is an electromagnetic ground conductivity instrument designed to map geological variations, groundwater contaminants, or any subsurface feature associated with changes in the ground conductivity. The EM31-MK2 creates a magnetic field that generates eddy currents in subsurface materials. These eddy currents have an associated secondary magnetic field with a magnitude and phase shift (relative to the primary field) that is dependent on the conductivity of the medium. The receiver coil measures the resultant effect of both primary and secondary fields. By comparing the signal at the receiver to that at the transmitter, the instrument records the components of the secondary field inphase (inphase data) and 90 degrees out of phase (quadrature/conductivity data) with the primary field. The inphase component approximates metal detection response and is measured in units of parts per thousand (ppt). The quadrature component, also referred to as terrain or apparent conductivity, is representative of the conductivity of subsurface materials and is measured in units of milliSiemens per meter (mS/m). Extremely high quadrature responses will be measured as

Holloman AFB, NM

TerranearPMC, LLC 6 March 2023 Contract No. W912PP-21-D-0003 Final negative mS/m responses. Since subsurface structures or excavation features typically have significantly higher or lower conductivities and inphase responses relative to the local undisturbed soils this makes the EM31-MK2 a good tool for delineating the lateral extent of potential subsurface utilities and other buried structures or debris.

Emlid Reach RS2 RTK-GNSS

The Emlid Reach RS2 RTK-GNSS was integrated with the EM61-MK2 and EM31-MK2 to provide sub-meter geophysical data accuracy. An additional rover was used to capture the positions of relevant site features. The RS2 receivers are multi-frequency GNSS receivers that can receive and process multiple signal types (including GPS, GLONASS, Galileo, and BeiDou) and can achieve sub-centimeter accuracy. A base station was set up over a known benchmark and connected to a rover to collect positioning data.

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TerranearPMC, LLC 7 March 2023 Contract No. W912PP-21-D-0003 Final

3.0 METHODOLOGY

3.1 DGM SURVEY ACTIVITIES

The EM61-MK2 survey was conducted in 4-Channel mode along profiles spaced nominally 10 ft apart on center, using a single EM61-MK2 sensor over nine 50 ft by 50 ft areas. The nine areas cover the borehole locations proposed by Jacobs. 4-Channel data were recorded in automatic mode at a rate of 5 readings/second.

The EM31-MK2 survey was conducted in the vertical dipole mode, and both quadrature (conductivity) and inphase (metallic) response data were recorded. Data were collected in automatic mode along profiles spaced nominally 15 ft apart and at a rate of 5 readings/second.

Positional data for the DGM surveys was maintained using an RTK-GNSS with dynamic real-time horizontal sub-meter accuracies.

The Emlid Reach RS2 RTK-GNSS was used by the DGM field team to establish the survey grid and provide positions of site features due to terrain and other metallic surface features.

Quality Control (QC) tests were performed to demonstrate project specific Measurement Quality Objectives (MQOs) were met as documented in the Geophysical Investigation Plan. The following QC tests were performed for each DGM sensor: static background, static spike, vibration (cable shake) and dynamic response. Additional QC checks were in place for data separation and survey coverage (lane spacing). A discussion of the QC results is presented in Section 5.0. QC results are presented in Attachment 2 Electronic Deliverables.

3.2 EM61-MK2 DGM DATA PROCESSING

DGM data collected over the survey area with the EM61-MK2 were processed by experienced geophysical data processors using Geosoft Oasis Montaj (V.9.10) (herein referred to as Geosoft). The processing procedures and data quality assurance steps were completed as follows:

Daily field notes were reviewed for observations provided by the field team and description of cultural features which might influence data quality and/or interpretation.

Raw XYZ files for production surveys and QC test files were imported into the Geosoft software and Geosoft GDB files were created.

Latitude and Longitude data was converted to Easting and Northing, New Mexico West State Plane, North American Datum 1983 (NAD83) CONUS, in units of US Survey Feet.

The latency correction was performed to correct for an inline positional shift which occurs due to a timing delay between the time of when the RTK-GNSS position data is collected, and the sensor data is collected. A latency correction of -0.25 seconds was applied to the EM61-MK2 data collected on March 5, 2023.

Both positioning and geophysical sensor data quality for the production data were evaluated in profile to identify and correct data spikes, sample separation gaps, and sensor drift.

The data sets were gridded using a maximum grid cell size of 2.5 ft. (1/4 lane spacing of 10 ft).

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TerranearPMC, LLC 8 March 2023 Contract No. W912PP-21-D-0003 Final

DGM data were checked for gaps within the Geosoft QC module. Gaps can be created due to equipment malfunction or physical obstructions. The only gaps observed were from obstructions such as vegetation.

The detection data were plotted using color coded contour intervals with the color bar legend posted on the map.

Plan-view color image maps were generated for interpretation and exported to Adobe Acrobat PDF format.

Processed Master Geosoft databases containing all project EM61-MK2 data were archived and securely stored with the digital project information.

3.3 EM31-MK2 DGM DATA PROCESSING

DGM data collected over the EM31-MK2 survey areas were processed by experienced geophysical data processors using Geosoft. The processing procedures and data QC steps were completed as follows:

Daily field notes were reviewed for observations provided by the field team and description of cultural features which might influence data quality and/or interpretation.

Raw XYZ files for production surveys and QC test files were imported into the Geosoft software and Geosoft GDB files were created.

Latitude and Longitude data was converted to Easting and Northing, New Mexico West State Plane, NAD83 CONUS, in units of US Survey Feet.

An RTK-GNSS receiver offsets of +1.33 ft or +1.08 ft on March 1, 2023, +1.25 ft or +1.15 ft on March 2-3, 2023, +1.28 ft or +1.10 ft on March 4, 2023 and +1.28 ft or +1.00 ft on March 5, 2023 were applied in Geosoft due to the position of the RTK-GNSS relative to the center of the EM31-MK2 sensor. Offset applied was determined by which field team member was operating the sensor. The offset is the distance of the sensor to the RTK-GNSS receiver, relative to the survey line.

A latency correction of -0.6 seconds on March 1, 2023, -1.0 seconds on March 2, 2023, -0.5 seconds on March 3, 2023, -0.5 seconds on March 4, 2023, and -0.4 seconds on March 5, 2023, were applied for the EM31-MK2. Latencies were calculated based on a latency test on the dynamic response tests and were applied to the positioning data. The latency correction was performed to correct for an inline positional shift which occurs due to a timing delay between the time of when the RTK-GNSS position data is collected, and the sensor data is collected.

Both positional and geophysical sensor data quality for the production data were evaluated in profile to identify and correct data spikes, sample separation gaps, and sensor drift.

Inphase data collected March 1-5, 2023, was leveled to remove varying background responses. Cultural features (electromagnetic noise) in the area likely influenced the static background levels. Additionally, the quadrature data collected on March 4, 2023, was also leveled.

The inphase and quadrature phase data sets were gridded using a maximum grid cell size of 3.75 ft. (1/4 lane spacing of 15 ft).

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TerranearPMC, LLC 9 March 2023 Contract No. W912PP-21-D-0003 Final

Gridded DGM data from the production surveys were checked for gaps within the Geosoft software. Gaps can be created due to equipment malfunction, poor field navigation, or physical obstructions. The only gaps observed were from obstructions within the survey area due to vegetation and terrain features such as arroyos that were navigated around.

The inphase and quadrature phase data were plotted using color coded contour intervals with the color bar legend posted on each map.

Plan-view color image maps were generated for interpretation and exported to Adobe Acrobat PDF format.

Processed Master Geosoft databases containing all project EM31-MK2 data were archived and securely stored with the digital project information.

3.4 QUALITY CONTROL

QC measures for this project included DGM Instrument and Positioning Systems QC to meet project specific MQOs. Requirements of all MQOs can be found in the Geophysical Investigation Plan (TPMC, 2023). QC results are summarized in Section 5.0, DGM Instrument and Positioning Systems QC Results.

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TerranearPMC, LLC 10 March 2023 Contract No. W912PP-21-D-0003 Final

4.0 RESULTS

4.1 SUMMARY OF WORK PERFORMED

On February 28, 2023 the geophysics team confirmed the validity of the benchmark at Pit 3 and established a new control point (TPMC-01) and staked out the survey grid across the site. DGM data collection was performed using the Geonics EM61-MK2 and Geonics EM31-MK2 instruments from March 1-5, 2023. Positioning control was obtained through RTK-GNSS positioning with better than submeter accuracy. The work was performed in accordance with the Geophysical Investigation Plan (TPMC, 2023). TPMC demobilized from the site on March 6, 2023.

4.2 MOBILIZATION AND SITE SETUP

TPMC mobilized personnel and equipment to the project site on February 27, 2023.

Prior to TMPC’s arrival, Jacobs and TPMC agreed upon a survey area derived from aerial photographs. Approximate extents of the DGM survey area are displayed in Figure 2.

4.3 DGM SURVEY ACTIVITIES

DGM data acquisition on the site was accomplished using the EM61-MK2 and EM31-MK2 sensors integrated with the Emlid Reach RS2 RTK-GNSS receiver as described in Section 2.0.

Comprehensive data coverage was achieved across the survey area.

4.4 DATA INTERPRETATION

After data processing was completed, the EM61-MK2 and EM31-MK2 response data were reviewed and interpreted by a TPMC geophysicist. All EM61-MK2 and EM31-MK2 results are presented on plates in Attachment 1.

Surface features visually observed in the field included: overhead powerlines, topographical mounds, arroyos, surface metal and vegetation. RTK-GNSS point of several surface features were taken and are included in Attachment 2. Due to the site being in a secure area TPMC was not permitted to take photographs. Several site photographs were taken on March 1, 2023 by a cleared security escort and are included in the Attachment 2 photo log.

Plate 1 shows the EM61-MK2 Channel 2 response. The mV response shows relatively low values indicating little metallic responses. No potential utilities or subsurface metallic debris were identified within the EM61-MK2 data. The nine proposed borehole locations are also plotted on map.

Plate 2 shows the EM31-MK2 inphase response. The map shows one area with slightly elevated responses in the SW corner which indicates there may be some subsurface metal.

There are no areas with greater or less than (+/-) a 5 ppt response. The SW-NE trending linear gap in the northwestern area is a road running through the survey area where data was not collected. Some of the inphase data collected on March 4, 2023, over the middle SW-NE trending linear gap, was not useable due to a bad cable connection. The cable was subsequently replaced, and the remaining data collection was good. Data collection was not conducted over the SW-NE trending southeastern linear gap shown due to schedule constraints and lower production rates resulting from vegetation and terrain. The nine proposed borehole locations are also plotted on map.

Holloman AFB, NM

TerranearPMC, LLC 11 March 2023 Contract No. W912PP-21-D-0003 Final

Plate 3 shows the EM31-MK2 Conductivity response. The map show areas with elevated responses greater than 20 mS/m and conductivity of approximately 5-20 mS/m across most of the site. The areas of higher conductivity do not appear in the inphase response, suggesting that the areas do not have metallic responses. The elevated conductivity areas could be soil/geologic related or could indicate trash/waste without a large amount of metallic content.

The nine proposed borehole locations are also plotted on map. The northwestern SW-NE trending linear gap is a road running through the survey area that data was not collected over.

Data collection was not conducted over the SW-NE trending southeastern linear gap shown due to schedule constraints and lower production rates resulting from vegetation and terrain.

Holloman AFB, NM

TerranearPMC, LLC 12 March 2023 Contract No. W912PP-21-D-0003 Final

5.0 DGM INSTRUMENTS AND POSITIONSING SYSTEMS QUALITY CONTROL RESULTS

The following QC tests were performed as part of the field survey. A brief discussion of the tests is provided as follows:

1. Equipment Warm-up. The EM61-MK2 and EM31-MK2 systems were turned on and allowed to warm up for a minimum of 10 minutes prior to use. Equipment warm-up was performed the first time an instrument was turned on for the day or had been turned off for longer than approximately 10 minutes.

2. RTK-GNSS Precision Check. Positional checks were performed at the start of each day for the Emlid Reach RS2 RTK-GNSS receiver. There were no issues identified during the Precision Check. All RTK-GNSS precision points met the MQO that all recorded positions will be consistently within +/- 5 ft of the initial measurement(s) recorded. RTK-GNSS Precision Check results are presented in Attachment 2.

3. Static Background. Static tests were performed by positioning the EM61-MK2 and EM31- MK2 in an area relatively free of metallic contacts and collecting data for at least one minute.

During this time, the instrument was held in a fixed position for one minute. The purpose of these tests was to assess background conditions and identify potential EM noise effects that may impact the sensor throughout each survey. Static results show that the background varied from day to day, likely due to cultural electromagnetic noise in the area. Data were leveled as needed. The EM31-MK2 AM Static Background test on March 4, 2023, showed that the data logger was not properly recording the inphase data due to a bad cable. After some data was collected the cable was replaced and there were no issues in the PM Static Background test. Inphase and quadrature data collected with the bad cable was closely reviewed and used only if it appeared unaffected. All static results are presented in Attachment 2.

4. Static Spike. Static spike tests were performed by positioning the EM61-MK2 in an area free of metallic contacts, placing a small Industry Standard Object (ISO) (1” x 4” steel pipe nipple) below the center of the bottom coil, and collecting data for at least one minute.

During this time, the instrument was held in a fixed position for one minute. The purpose of these tests was to assess geophysical response to a known metallic item versus background site conditions and identify potential EM noise effects that may impact the sensor throughout each survey. No significant potential noise impacts to identifying a metallic object was identified during the static spike testing. All static spike results are presented in Attachment 2.

5. Vibration Test (Cable Shake). This test checked the response of instruments to vibration and the shaking of the instrument cables during data collection. The EM61-MK2 and EM31- MK2 were checked for adverse effects caused by vibrations in the system’s cables. The vibration test was conducted at the beginning of the survey workday. The EM31-MK2 Cable Shake test on March 4, 2023 indicated the data logger was not properly recording the inphase data. The cable was replaced during the day and the Cable Shake test repeated during the PM QC tests. The inphase data collected with the bad cable on March 4, 2023, was not used. No additional issues were identified during vibration testing throughout the field effort. All Vibration Test results are presented in Attachment 2.

6. Dynamic Response The dynamic response test for the EM61-MK2 was completed by walking over a small ISO in opposing directions. Dynamic response tests for the EM31-MK2 were completed by walking the EM31 across the aluminum shipping container in opposing

Holloman AFB, NM

TerranearPMC, LLC 13 March 2023 Contract No. W912PP-21-D-0003 Final directions. The EM31-MK2 AM dynamic test on March 4, 2023, showed that the sensor or data logger was not properly recording the inphase data. The cable was replaced during the day and the PM Dynamic Response test was successful. Inphase data collected with the bad cable was not used and quadrature data was closely reviewed and used if it appeared unaffected. Observing the responses, the other tests show to be qualitatively consistent and repeatable. All Dynamic Response results are presented in Attachment 2.

7. Data Separation and Spacing: The MQO for data separation and spacing (along each survey transect) is to have sufficient inline density along each transect to fulfill the survey objectives. The MQO is with a point-to-point spacing of <5 ft, unless an obstruction or hazard is present, and the operator cannot navigate over it. Gaps observed were due to vegetation and terrain obstacles that had to be navigated around. This was evaluated by verifying that all the DGM data collected and interpreted met this standard using the Geosoft sample separation QC Module. QC performed showed the down line separation met the established MQOs. The EM61-MK2 and EM31-MK2 Data Separation and Spacing Test results are presented in Attachment 2.

8. Survey Coverage (Lane Spacing): The MQO for lane spacing is to maintain appropriate lane spacing to provide an effective survey coverage with the EM61-MK2 and EM31-MK2 to delineate the lateral extent of disturbed soils and potential subsurface structures/debris. The MQO is to have no crossline accessible portions of the survey area. The MQO criterion for the EM61-MK2 is that the lane

The measurement performance criterion for the EM31-MK2 is that the lane spacing is no greater than 1.5x the intended lane spacing of 15 ft. This was evaluated using the Geosoft coverage QC Module to verify that all the DGM data collected and interpreted met this requirement, except for locations where obstructions prohibited such coverage. It was determined that the data coverage MQOs were met for both geophysical systems. EM61-MK2 and EM31-MK2 Survey Coverage Test results are presented in Attachment 2.

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TerranearPMC, LLC 14 March 2023 Contract No. W912PP-21-D-0003 Final

6.0 CONCLUSIONS AND LIMITATIONS

This report details the procedures and results of the DGM survey operations completed by TPMC at the proposed site of the Indoor Target Flip Facility, located at WSMR and adjacent to Holloman AFB, Alamogordo, New Mexico. The objective of the geophysical survey was to ensure that any buried utilities or debris can be identified up to a maximum of 6 ft in depth or the full depth of expected excavation required at the site. Minimal information exists on site history and current site conditions. As a result, the geophysical survey was conducted primarily as a precautionary measure, the results of which will assist in minimizing cost and schedule impacts to the facility construction.

DGM surveys were completed using the EM61-MK2 and EM31-MK2 detectors. It was determined that the data coverage obtained with the EM31-MK2 and EM61-MK2 is sufficient for the current stage of the project since the planned borehole locations were adequately surveyed.

Data positioning was accomplished using RTK-GNSS. In accordance with the Geophysical Investigation Plan, all DGM data quality was monitored via QC steps which entailed daily instrument tests. It was determined that all MQOs were met during the investigation.

The results of both the EM61-MK2 and EM31-MK2 surveys indicate little potential for subsurface metal being present on site. The EM-61MK2 results indicate little response in the nine areas surveyed.

The EM31-MK2 inphase and conductivity (quadrature) data showed one area of slightly elevated inphase response in the SW area and several areas of slightly elevated conductivity response. Inphase responses indicate there may be subsurface metallic items in the SW area.

Areas of elevated conductivity may suggest changes in soil/geology or disturbed soils or buried trash/waste with little metallic debris.

Disclaimer: Although geophysical methods provide a high level of assurance for location of subsurface objects, the possibility exists that not all features can or will be identified. The parties understand that no method can be as exact and reliable as an actual excavation and physical examination that thoroughly covers the surveyed site. Therefore, TPMC will not be liable for any damages that occur from excavations by others based on the results and deliverables generated from this subsurface imaging and mapping project. Due caution should be used when performing any subsurface excavation based on results interpreted from this geophysical scanning and mapping. Client understands and agrees that any action client may take based on the data and information supplied hereunder shall be at client’s own responsibility and sole risk.

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TerranearPMC, LLC 15 March 2023 Contract No. W912PP-21-D-0003 Final

7.0 REFERENCES

TPMC, 2023. Geophysical Investigation Plan, Indoor Target Flip Facility, Holloman AFB, New Mexico.

ATTACHMENT 1

LETTER-SIZE MOSAIC PLATES(S) SHOWING DGM

RESULTS

Plate 1 EM61-MK2 Channel 2 Response Plate 2 EM31-MK2 Inphase Response Plate 3 EM31-MK2 Conductivity Response

ATTACHMENT 2

ELECTRONIC DELIVERABLES (INCLUDES ALL DATA AND

DELIVERABLES)

**Note: Electronic Deliverables were uploaded to the Jacobs FTP site.

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-7 , B

-9 Up pe rm os t c la y la ye r i n th e in d ic at ed b or in gs

C al ifo rn ia B ea rin g Ra tio (C

BR

B-

4, B

-8 C om po sit e sa m pl es o bt ai ne d fro m fe et

B G

S.

M od ifi ed

P ro ct or

B-

4, B

-8 C om po sit e sa m pl es o bt ai ne d fr om fe et

B G

S.

pH

B- 1, B -2

, B -3

, B -8

, B -9

C om po sit e sa m pl es ta ke n fro m fe et B

G S.

D ry

D en sit y

N o sa m pl es h el d fo rm d ur in g re tri ev al

Pe rc ol at io n

Te st

P-

Pe rfo rm ed d ur in g fie ld w or k.