2-1 2.0 STATIC TEST This Section Describes the Objectives

2.0 STATIC TEST

This section describes the objectives, procedures, and results of the Static Test completed at Fort Ord, California, as part of the ODDS.

2.1 INTRODUCTION AND PURPOSE

The Static Test, the ODDS first phase, consisted of collecting digital geophysical survey data in free-air over selected inert OE items at incrementally greater depths. This was accomplished by constructing a nonmetallic test stand approximately 10 feet high with mechanisms to suspend OE items at different orientations and depths (within 1/32 inch) below the surface of the stand. Inert ordnance items typical of Fort Ord were used during the Static Test. Pictures of these items, the test stand and the Static Test operations are provided in Appendix A. The Static Test was conducted between June 2 and June 23, 2000 at Fort Ord using four geophysical detectors, 1) EM61, 2) EM61-HH, 3) G-858, and 4) GEM-3 as proposed in the ODDS Work Plan (USA Environmental Inc., May 2000).

2.1.1 Objectives

The objectives of the Static Test were to determine, establish, and document: 1. The range of detector readings indexed by OE item depth, orientation and detector type. 2. Free-air detector readings and signal profiles over OE items at a variety of incremental depths. 3. The range of detectable depths and horizontal distances for typical OE items found at Fort Ord using different types of detectors. 4. Baseline capabilities for mature-, new- and emerging-technology detectors, without interference from variable ground surface and soil conditions, compared to detectors currently in use at Fort Ord. 2.1.2 Background

The Static Test was conducted using the four detectors identified by the USAESCH OE Center of Expertise as having potential for OE detection at Fort Ord. A full description and rationale for selecting these detectors appears in Appendix E of the ODDS Final Work Plan (USA Environmental Inc., May, 2000). The selected systems represent a range of technologies that have consistently provided the highest probability of detection (PD) and lowest false alarm rate (FAR) on ordnance test grids and live sites. Each has proven effectiveness in detecting and locating buried OE items.

Detector Manufacturer and Model Type 1. Geonics Model EM61 (TDEM)

2-1 ODDS REPORT

2. Geonics Model EM61-HH (TDEM) 3. Geometrics Model G-858 (Cesium Vapor) (Magnetometer) 4. Geophex Model GEM-3 (40 cm coil) (FDEM) All of these instruments are man-portable and provide spatial response data as the detector is moved over an object. Positional data can be collected by three different methods: (1) continuous mode, whereby the data are collected on selected time intervals and the operator marks the data based on positional fiducials and the data are fitted to a known distance; (2) wheel mode, whereby the digital data are collected and marked by the turning of a survey wheel attached to the instrument; and (3) GPS mode, whereby the detector and GPS positional data as well as the sensor data are collected on selected time intervals. All of these methods allow for the development of two-dimensional analysis as well as generating line profiles from the collected data.

Data collected from these instruments provides information on the capabilities for “families” of instruments that measure a specific physical property (such as magnetic gradient, total magnetic field, etc.) by means of recording a digital signal response. These four instruments were used as examples for families of equipment that measure either a single time window of a time domain EM response (EM61), two or more time windows of a time domain EM response (EM61-HH), total magnetic fields and magnetic field gradients using cesium vapor sensor technology (G-858), or frequency domain EM response (GEM-3).

Analog instruments such as the Schonstedt were not used during the Static Test since there is no consistent method for determining the magnitude and shape of the response. However, analog instruments were used during the Seeded Test and Field Trial Site phases of the ODDS.

2.2 ORDNANCE USED IN STATIC TEST

A total of sixteen OE items were used during the Static Test. Table 2-1 is a list of the OE items tested and the dimensions, weights and depth of penetration in sand for these items. [It should be noted that, for the sake of brevity and consistency, shortened descriptions of OE items have been used throughout the document. The full description of the OE items can be found in the Acronyms and Abbreviations section at the end of the table of contents.] All but two of the OE items were inert items obtained from previous OE investigations at Fort Ord. The 105mm and 155mm inert projectiles were collected from Fort Irwin, CA. Most of the items were rusted but in good, intact condition. Pictures of the OE items used in the testing are presented in Appendix A. The categories in Table 2-1 are discussed in Section 2.5.1.

2-2 ODDS REPORT

Table 2-1 Characterization of OE Items Used in Static Tests Ordnance Detection and Discrimination Study Fort Ord, California ODDS REPORT Depth of Depth of Diameter Length Weight Penetration Penetration Ordnance Item (Inches) (Inches) (lbs.) In Sanda Plus One Footb Categorye

14.5mm Projectile 0.57 2.55 0.152 0.2 1.2 II 22mm subcaliber 0.87 7 0.625 1.4 2.4 III

35mm Subcaliber 0.75 7.5 0.32 0.5 1.5 II 37mm Projectile 1.46 4.5 1.75 3.9 4.9 V

M9/M11 Grenade 2.25 3.5 1 0.1 1.1 II 60mm Projectile 2.36 7 4.25 1.1 2.1 III 2.36-inch Rocket 2.36 19.5 3.25 0.4 1.4 II 75mm Projectile 3 11 12 3.9 4.9 V 81mm Projectile 3.18 11 5.25 2.7 3.7 IV f

2 81mm Illumination 3.18 25 10.7 NA NA IV - 3 3.5-inch Rocket 3.5 23.6 9 0.8 1.8 II Signal Illumination Flare 1.5 10 0.53 0 1 I 90mm Projectile 4 9.5 22.3 2 3 III 105mm Projectiled 4.13 16.8 NA 7.7 8.7 IX 155mm Projectiled 6.1 26.93 NA 14 15 X Stokes Mortar 3 14 8.25 3.3 4.3 V MKII Grenade 4.75 4.75 1 0 1 I a Penetration Depths were taken from Table 4.1-1 of the Former Fort Ord Phase II EE/CA, April 1998. b Includes a one foot cover of post deposition material c Category of munitions determined by rounding up to the nearest foot d Used smoke OE Item to simulate shape of high explosive version of item. e See Section 2.5.1 of text. f Category depth for 81mm Illumination based on potential penetration of “dud” item NA - Data not available

2.3 STATIC TEST PROCEDURES

The following subsections describe the Static Test area setup, test stand construction and test procedures.

2.3.1 Static Test Area Before placing the Static Test stand in the test area, the OE contractor, USA, performed a magnetometer clearance of the entire area removing detected metal debris to a depth of four feet. Hand-held magnetometers (Schonstedt Model GA-52/Cx) were used in the clearance process. Ferrous metallic items detected using the Schonstedts were removed from the area. During the clearance process, a number of live UXO items were identified and detonated in place. A work plan variance was developed as the presence of UXO affected the Static Test schedule originally proposed in the Work Plan. Work plan variance forms are provided in Appendix B Tab 4.

Following the clearance by USA, EM61 and G-858 magnetometer surveys were conducted over the test stand area. Seventeen EM and two magnetometer anomalies were identified, located in the field, and intrusively investigated. Metal sources were removed. Results of the investigation are presented in Appendix B Tab 6. Once identified anomalies were removed, the test stand was placed with the longest dimension of the stand oriented in a magnetic north-south direction.

2.3.2 Test Stand Construction

The test stand was constructed entirely of a nonmetallic, nonconductive polymer (see Appendix B Tab 5 for specifications). All supporting beams, the floor of the stand, bolts, and nuts were also of polymer material. A polymer frame and ordnance holder were constructed to allow the raising and lowering of the OE test items at fixed distances or intervals from the sensors. The dimensions of the deck were approximately 8 feet wide and 12 feet long and it was elevated approximately 10 feet above ground surface. Photographs showing the Static Test stand are presented in Appendix A.

Before Static Testing was performed, conductivity and magnetic response measurements were taken on the stand platform to ensure that the construction materials were non-responsive to the instruments being tested. Responses were within the background range of the instruments. Three 8-foot long profile lines were marked on the platform, with fiducial marks at the start, middle and end of each line. The centerline was positioned directly over the center of the platform; two profile lines were located 2 feet on either side of the centerline profile. The center of the ordnance holder was constructed so that the center of the holder was located directly under the mid-point of the centerline.

A work plan variance (see Appendix B Tab 4) was prepared to describe two modifications to the test procedures because of stand construction limitations. Originally, the side profiles were to be spaced 2.5 feet on either side of the centerline; however,

2-4 ODDS REPORT

because of the addition of safety side rails on the platform the profiles were located on 2-foot centers. This minor change did not affect the quality of the test.

2.3.3 Static Test The following subsections describe the Static Test procedures.

2.3.3.1 Background and Instrument Functional Testing Procedures Static testing procedures included performing background and functionality tests of the equipment at the start and end of each test session. Background testing consisted of collecting electronic digital data along each of the marked profile lines within the area with no metallic objects in the ordnance holder. Data were recorded electronically and reviewed to determine baseline and expected noise levels of each of the instruments being tested. Equipment functionality tests consisted of performing single line profiles over a designated metallic sphere and recording the data digitally. The metallic sphere was an inert M62 grenade approximately two inches in diameter. This item was placed in the same position and location each time a measurement was performed. At the time of the Static Testing, data from the functionality test were reviewed on-site and the peak values were compared to previously collected data to ensure consistency in response of the instruments. Data from both the daily background and functionality tests for the instruments tested are presented in Appendix B Tab 2. Tables 2-2 and 2-3 are summaries of the instrument background and functionality tests performed. These tables show the minimum and maximum sensor responses for background conditions and over a known metal object.

2.3.3.2 OE Static Test Procedures

After completing daily background and functional testing, OE static measurements were taken. The types of OE measurements to be conducted were planned daily. OE items were wrapped in nonconducting, nonmetallic foam rubber, placed in the ordnance holder, and then rotated into the desired measurement position. In the horizontal position, the item was centered on the dimensional midpoint of the item. A permanent measuring tape was extended from the top of the platform floor (0 foot depth) to the top of the positioned OE item. The depth of the OE item was measured from the platform floor (the “ground”) to the top of the item (as it would be done in the field during excavation). The ordnance holder was adjusted until the top of the OE item was at the required measurement depth.

On-site records consisted of recording the time-of-day and electronic file name for each of the OE items. Electronic file names indicate the instrument being used, OE item, OE orientation, and depth of OE item below the test stand. Table 2-4 shows the file naming procedure. At the start of each test, the time-of-day along with a file name were recorded by the record keeper and communicated verbally to the equipment operator for input into the electronic file.

2-5 ODDS REPORT

Table 2-2 Instrument Background Signal Responses Fort Ord, California

Top Coil (mV) Bottom Coil (mV) EM61 Date Maximum Minimum Difference Maximum Minimum Difference EM61 6/5/2000 AM 1.5 -0.18 0.75 -0.75 6/5/2000 AM 1.5 -0.18 1.68 0.75 -0.75 1.5 6/5/2000 PM 1.5 0 1.5 1.5 0 1.5 6/8/2000 AM 1.5 0 1.5 0.75 0 0.75 6/8/2000 PM 0 -0.55 0.55 0.75 -0.75 1.5 6/12/2000 AM -0.18 -0.93 0.75 0.75 -0.18 0.93 6/12/2000 PM 0.19 -0.93 1.12 0.75 -0.75 1.5

Early Channel (mV) Late Channel (mV) EM61 -HH Date Maximum Minimum Difference Maximum Minimum Difference 6/12/2000 AM 0.75 -1.3 2.05 0.55 -1.5 2.05 6/12/2000 PM 1.5 -0.75 2.25 0 -0.75 0.75 6/13/2000 AM 0.75 -1.68 2.43 0.75 0 0.75 6/13/2000 PM 1.5 -1.5 3 0 -0.75 0.75 6/14/2000 AM 0.37 -1.87 2.24 -0.18 -0.75 0.57 6/14/2000 PM 0.75 -1.5 2.25 0.56 0 0.56 Vertical Gradient (nT / ft) G-858 Date Maximum Minimum Difference 6/6/2000 AM 1.127 -1.011 2.138 6/6/2000 PM 1.956 -3.093 5.049 6/7/2000 AM 0.947 -1.022 1.969 6/7/2000 PM 2.095 -1.341 3.436 6/8/2000 AM 1.249 -0.818 2.067 6/8/2000 PM 1.445 -1.6 3.045 Quadrature Sum (ppm) GEM-3 Date Maximum Minimum Difference 6/20/00 AM 0.83 -0.36 1.19 6/20/00 PM 0.67 -0.26 0.93 6/21/00 AM 0.68 -0.42 1.1 6/21/00 PM 0.47 -0.47 0.94 6/22/00 AM 0.65 -0.52 1.17 6/22/00 PM 1.22 -0.25 1.47

2-6 ODDS REPORT

Table 2-3 Instrument Functionality Signal Response on an M62 Hand Grenade Ordnance Detection and Discrimination Study Fort Ord, California Top Coil Response

(mV) Bottom Coil Response (mV) EM61 Date Maximum Maximum 6/5/2000 AM 1.5 0.75 6/5/2000 AM 24 24.94 6/5/2000 PM 24.18 25.12 6/8/2000 AM 24.75 25.5 6/8/2000 PM (a) 24 24 6/8/2000 PM (b) 23.81 23.44 6/12/2000 AM 24 24.94 6/12/2000 PM 24.18 25.12

Early Channel (mV) Late Channel (mV) EM61 -HH Date Maximum Maximum 6/12/2000 AM 8632 1803 6/12/2000 PM 9198 2197 6/13/2000 AM 9243 2280 6/13/2000 PM 8250 1661 6/14/2000 AM 8306 1807 6/14/2000 PM 8790 2025 Vertical Gradient (nT \ ft) G-858 Date Maximum 6/6/2000 AM 49.632 6/6/2000 PM 35.859 6/7/2000 AM 49.191 6/7/2000 PM 39.731 6/8/2000 AM 35.079 6/8/2000 PM 43.51 330 Hz inphase (ppm) GEM-3 Date Minimum 6/20/2000 AM -408.13 6/20/2000 PM -413.22 6/21/2000 AM -401.19 6/21/2000 PM 1 -300.26 6/22/2000 AM -410.66 6/22/2000 PM -413.38 1 The GEM -3 sensor was 2 inches higher during this check.

2-7 ODDS REPORT

Table 2-4 File Name Designation Formula Ordnance Detection and Discrimination Study Fort Ord, California

Instrument EM61 E EM61-HH (hand held) H G-858 M GEM-3 G

Munition Abbreviation

14.5 mm Projectile 145 22mm Projectile 22S 35mm Projectile 35S 37mm Projectile 37P M9 Grenade M9G 2.36" Rocket 236 75mm Projectile 75P 81mm Projectile 81P 3.5" Rocket350 Sig.Illum SIF SAMPLE FILE NAME: 81 Illum. 81I E 145 0 A0 Mk2 Grenade M2G 155mm Projectile 155 The above file name belongs STOKES STO to the signature from an EM61 90mm Projectile 90P for a 14.5mm 60mm Projectile 60P Projectile at a 0 degree 105mm Projectile 105 rotation and a depth of 0.5 feet

Rotation

EM61 0 (horizontal) =0 EM61 90 (vertical) = 9 EM61-HH 0 (horizontal) = 0 EM61-HH 90 (vertical) = 9 G-858 60 = 0 G-858 150 = 9

Depth (In feet)

0.5 = A0 1.0 = A1 1.5 = A2 2.0 = B1 3.0 = C1 4.0 = D1 5.0 = E1 6.0 = F1 7.0 = G1 8.0 = H1 9.0 = I1

2-8 ODDS REPORT

OE item measurements consisted of collecting three 8-foot profile measurements: centerline and two side profiles along the marked platform (each profile being 2 feet to either side of the centerline). All profile measurement data were collected in a south to north direction. Once the measurements were completed, the ordnance holder was adjusted to vary the inclination of the OE item, change the OE item, or adjust the OE item for a new depth measurement. All measurements were taken with one instrument until completed for the desired depths. These procedures were repeated until all the OE items were measured at the required depths or until it was determined that the OE item was at a depth where the instrument response was at the background level.

2.4 STATIC TEST RESULTS Field documentation (included in Appendix B Tab 2) includes test records for each background test, functionality test, instrument record forms, and OE item profile forms. Digital electronic files for each of the instruments included raw files (downloaded files from the detector recorder), combined files (uncorrected files from the detector recorder but processed into ASCII files), and profile files (corrected Microsoft Excel files with graphical profiles). Static Test profiles are included in Appendix B Tab 1, organized by OE item tested. TDEM instrument test results are reported for both the bottom and top receiving coils for the EM61 and for early and late time windows for the EM61-HH. G- 858 results are reported for the vertical magnetic gradient and total magnetic field and GEM-3 (FDEM) data are reported for both in-phase and quadrature phase over five frequencies.

2.5 STATIC TEST ANALYS ES The following subsections describe the procedures used during the Static Test analyses.

2.5.1 Categorization of OE Items

The calculated maximum penetration depths for OE items and the ODDS Static Test results (measured depths of detection) were used to categorize the OE. This grouping was used to determine the depth and orientation of the buried OE items for the second phase of the ODDS, the Seeded Test. The following sections describe the OE grouping procedure.

2.5.1.1 Assign OE Item Categories and Groups

Each OE item was placed in an OE category and group based on its maximum penetration depth (USAESCH, 1998) and individual instrument readings. The maximum penetration depth for each OE item was determined by the Huntsville Corp of Engineers based on a calculated penetration assuming muzzle velocity, entry into the ground at a perpendicular angle and other “worst case factors.” Actual penetration depths at Fort Ord have been found to be less (USA Environmental Inc., April, 2001). Separate OE categorization tables were developed for the EM61, EM61-HH, G-858 and GEM-3 as

2-9 ODDS REPORT

shown in Tables 2-5 through 2-8. These tables include the estimated detection depths and OE Group for the best and worst orientation. The categories and groups are:

· Categories I through X classify OE items based on calculated penetration capabilities at the time of impact in sand plus 1 foot to allow for soil deposition. Individual categories are identified with a roman numeral equal to the maximum penetration depth plus 1 foot (rounded up to the next whole number). For example, an item with a penetration depth of 0.6 foot would then have 1 foot added to this penetration depth for a total of 1.6 feet and placed in Category II. · Groups A through C classify OE items based on strength of signal. Each OE item was assigned to groups A through C within its category based on the detection readings taken by each detector in the Static Test at the item’s maximum depth of penetration plus 1 foot. An OE item was grouped according to the following: 1. Group A if the item was not detected at the item’s calculated maximum depth of penetration plus 1 foot. 2. Group B if the item was detected at the item’s calculated maximum penetration depth plus 1 foot and the signal strength was less than five times the estimated background noise level (signal due to geologic features, terrain, or produced by the presence or operation of the instrument itself). 3. Group C if the item was detected at the item’s calculated maximum penetration depth plus 1 foot and the signal strength was more than five times the estimated background noise level. A five times background noise level was used to distinguish values slightly higher than background from higher response anomalies. This value was chosen based on empirical field data as an anomaly that should be distinguishable from increased background noise caused by terrain or local geologic conditions. This 5-times (5X) was used as a simple classification tool for analysis. This was not a criteria for target selection.

2.5.1.2 Final Category and Detection Matrix

The final categorization step was to develop a combined matrix by category for all detectors and OE items. Table 2-9 combines the category and group data from each sensor. As the table shows, the calculated depth of penetration may exceed the depth of detection. For example, the 37mm projectile was detected to a depth of 1 to 2 feet depending on the instrument and the orientation; however, the calculated depth of penetration is 5 feet. In other cases, the OE item, for example the MKII grenade, was found with all instruments at the calculated depth of penetration.

2-10 ODDS REPORT

Table 2-5 EM61 OE Item Categorization Matrix Ordnance Detection and Discrimination Study Fort Ord, California

Instr. Type: EM61 1 Meter x 1 Meter, Cart ITEM MAX reading at deepest MAX reading at deepest Max. Depth of OE CATEGORY/GROUP2 depth for best orientation depth for worst orientation 1 ODDS REPORT Detection Best/Worst Orientation (Feet), Best/Worst Orientation Reading3 Orient. Reading3 Orient.

14.5mm Projectile 1.49 < 1 0.5/0 IIA/IIA MKII Grenade 4.68 2.25 1/1 IB/IB Signal Illumination Flare 8.67 7.12 1/1 IC/IC M9/M11 Grenade 2.25 1 2/2 IIB/IIB 2.36-inch Rocket 9.94 4.5 2/2 IIC/IIB 35mm Subcaliber 5.25 1.5 1/1 IIA/IIA 22mm Projectile 2.11 1.17 1/1 IIIA/IIIA 2 60mm Projectile 2.25 2.81 3/2 IIIB/IIIA -

11 3.5-inch Rocket 1.7 5.5 4/3 IIC/IIC

90mm Projectile 1.5 2.25 4/3 IIIB/IIIB Stokes Mortar 1.87 2.25 4/3 VA/VA 37mm Projectile 3.75 3.18 1.5/1 VA/VA 81mm Projectile 3.7 4.5 3/2 IVA/IVA 81mm Illumination 3 2.81 3/3 IVA/IVA 75mm Projectile 12 2.81 2/2 VA/VA 105mm Projectile 3.18 1.5 4/4 IXA/IXA 155mm Projectile 1.5 1.5 6/6 XA/XA 1 Maximum depth of detection is equal to the deepest depth tested where the item was detected or the maximum depth of penetration. If the item was detected at the depth of penetration, the reading at the depth of penetration is shown. 2 Category is the calculated maximum depth of penetration in sand plus one foot for soil cover, rounded to the nearest foot presented in Fort Ord Phase II EE/CA Report April 1998. OE Groups defined in Section 2.5.1.1 in this report. 3 Readings are from the bottom channel of the EM61 in millivolts Indicates vertical orientation of munition with point down Indicates horizontal orientation of munition with point oriented magnetic north

Table 2-6 EM61-HH OE Item Categorization Matrix Ordnance Detection and Discrimination Study Fort Ord, California

ODDS REPORT Instr. Type: EM61-HH ITEM MAX reading at deepest MAX reading at deepest Max. Depth of OE CATEGORY/GROUP2 depth for best orientation depth for worst orientation Detection1 (Feet), Best/Worst Orientation Best/Worst Orientation

Reading3 Orient. Reading3 Orient. 14.5mm Projectile 1.5 2.81 1.5/0.5 IIB/IIA MKII Grenade 2.25 1.31 1.5/1.5 IB/IB Signal Illumination Flare 16.5 10.31 1/1 IC/IC M9/M11 Grenade 1.31 2.62 2/1.5 IIB/IIA 2.36-inch Rocket 5.43 3.74 2/2 IIC/IIB 2 35mm Subcaliber 3.55 1.31 2/1.5 IIB/IIA - 12 22mm Projectile 1.69 2.81 1.5/1 IIIA/IIIA

60mm Projectile 2.25 4.31 3/1.5 IIB/IIA 3.5-inch Rocket 20.25 15.37 1.5/1.5 IIA/IIA 90mm Projectile 2.06 5.25 3/2 IIIB/IIA Stokes Mortar 1.49 6 3/2 IIIA/IIIA 37mm Projectile 1.68 6.92 2/1.5 VA/VA 81mm Projectile 5.81 3.37 2/2 IVA/IVA 81mm Illumination 1.5 1.31 3/3 IVA/IVA 75mm Projectile 7.5 4.31 2/2 VA/VA 105mm Projectile 3 1.5 3/2 IXA/IXA 155mm Projectile 2.06 1.31 4/4 XA/XA 1 Maximum depth of detection is equal to the deepest depth tested where the item was detected or the maximum depth of penetration. If the item was detected at the depth of penetration, the reading at the depth of penetration is shown. 2 Category is the calculated maximum depth of penetration in sand plus one foot for soil cover, rounded to the nearest foot presented in Fort Ord Phase II EE/CA Report April 1998. OE Groups defined in Section 2.5.1.1 in this report. 3 Readings are from the late channel of the EM61-HH in millivolts Indicates vertical orientation of munition with point down Indicates horizontal orientation of munition with point oriented magnetic north

Table 2-7 G-858OE Item Categorization Matrix Ordnance Detection and Discrimination Study Fort Ord, California

ODDS REPORT Instr. Type: G-858, Vertical Gradient (bottom sensor minus top sensor) ITEM MAX reading at deepest MAX reading at deepest depth Max. Depth of OE CATEGORY/GROUP2 depth for best orientation for worst orientation Detection1 Best/Worst Orientation (Feet),

Best/Worst Orientation

Reading3 Orient. Reading3 Orient. 14.5mm Projectile <0.5 <0.5 0/0 IIA/IIA MKII Grenade 3.793 3.609 1/1 IB/IB 2

- Signal Illumination Flare 2.456 1.154 1/1 IB/IB 13 M9/M11 Grenade 2.02 3.325 2/1.5 IIB/IIA

2.36-inch Rocket 8.539 5.423 3/3 IIC/IIC 35mm Subcaliber 0.357 -6.522 0.5/0.5 IIA/IIA 22mm Projectile 1.261 1.049 1.5/1.5 IIIA/IIIA 60mm Projectile 1.251 3.753 3/2 IIIB/IIIA 3.5-inch Rocket 6.655 4.814 4/4 IIC/IIC 90mm Projectile 1.778 1.216 5/5 IIIB/IIIB Stokes Mortar 2.087 1.648 6/6 VB/VB 37mm Projectile 2.551 3.897 1.5/1 VA/VA 81mm Projectile 1.475 1.377 5/4 IVB/IVB 81mm Illumination 4.225 1.303 4/4 IVB/IVB 75mm Projectile 2.194 1.236 4/4 VA/VA 105mm Projectile -3.058 -3.793 7/6 IXA/IXA 155mm Projectile 7.497 5.115 7/7 XA/XA 1 Maximum depth of detection is equal to the deepest depth tested where the item was detected or the maximum depth of penetration. If the item was detected at the depth of penetration, the reading at the depth of penetration is shown. 2 Category is the calculated maximum depth of penetration in sand plus one foot for soil cover, rounded to the nearest foot presented in Fort Ord Phase II EE/CA Report April 1998. OE Groups defined in Section 2.5.1.1 in this report. 3 Readings are from the vertical gradient (bottom-top sensor) in nT/ft. Indicates 60 degree orientation of munition with point oriented magnetic north Indicates 150 degree orientation of munition with point oriented south

Table 2-8 GEM-3 OE Item Categorization Matrix Ordnance Detection and Discrimination Study Fort Ord, California

Instr. Type: GEM-3 40-cm dia head ITEM MAX reading at deepest MAX reading at deepest depth Max. Depth of OE ODDS REPORT depth for best orientation for worst orientation Detection1 (Feet), CATEGORY/GROUP2 Best/Worst Best/Worst Orientation Orientation

3 3

Reading Orient. Reading Orient. 14.5mm Projectile 1 2.2 2/1.5 IIB/IIA MKII Grenade 8.2 7.8 2/2 IC/IC Signal Illumination Flare 9.2 6.7 2/2 IC/IC M9/M11 Grenade 12.1 9 2/2 IIC/IIC 2

- 2.36-inch Rocket 8.3 7.9 2.5/2.5 IIC/IIC 14 35mm Subcaliber 6 3.4 2/2 IIC/IIB 22mm Projectile 4.1 3 2/2 IIIA/IIIA 60mm Projectile 3 2.1 3/3 IIIB/IIIB 3.5-inch Rocket 6.7 4.1 3/3 IIC/IIC 90mm Projectile 1.5 1.7 4/4 IIIC/IIIC Stokes Mortar 1.6 1.2 4/3 VA/VA 37mm Projectile 6.4 6 2/2 VA/VA 81mm Projectile 3.9 3.8 3/2 IVA/IVA 81mm Illumination 2.6 2 3/4 IVA/IVA 75mm Projectile 5.1 5.1 3/3 VA/VA 105mm Projectile 2.6 2.3 4/4 IXA/IXA 155mm Projectile 1.8 1.5 5/5 XA/XA 1 Maximum depth of detection is equal to the deepest depth tested where the item was detected or the maximum depth of penetration. If the item was detected at the depth of penetration, the reading at the depth of penetration is shown. 2 Category is the calculated maximum depth of penetration in sand plus one foot for soil cover, rounded to the nearest foot presented in Fort Ord Phase II EE/CA Report April 1998. OE Groups defined in Section 2.5.1.1 in this report. 3 Readings are quadrature sum readings from five frequencies in ppm Indicates vertical orientation of munition with point down Indicates horizontal orientation of munition with point oriented magnetic north

2.5.2 Detection Depth by OE Items and Instrument Type

Table 2-9 summarizes the OE categories for each instrument. Figures 2-1 and 2-2 represent the relative depths at which each instrument could detect each OE test item, at the best and worst orientations. Group designations were based on visual inspection of the test stand profiles. For quantitative comparison, the signal-to-noise ratio (SNR) was calculated. The signal was defined as the highest peak signal (or largest absolute peak value for magnetic profiles). The noise level was defined for each instrument as the standard deviation of all the data collected as background profiles on the test stand. In the following analysis, an anomaly is described as significant if the SNR is greater than five. For many of the smaller items, the GEM-3 and EM61-HH had significant anomalies at depths greater than the EM61 and G-858. However, the EM61 and G- 858 had significant anomalies for several of the larger items at the greatest depths.

2.5.2.1 Categories I and II OE Items Of the 17 items tested, 7 fall into Category I or II, indicating that they are unlikely to be encountered greater than 2 feet deep. Generally, the two EM sensors with smaller coils, the EM61-HH and the GEM-3, performed best in the Static Test over these items. All four instruments detected the MKII grenade, signal illumination flare, 2.36-inch rocket, and 3.5-inch rocket with distinctive anomalies at their category depths and are not discussed below. The following subsections highlight observations from tests on the ordnance item in Categories I and II.

14.5mm Projectile · Only the GEM-3 had a significant anomaly over the 14.5mm projectile at 2 feet and in only one orientation. However, the GEM-3 anomalies at 1.5 feet were significant in both vertical and horizontal orientations. This depth is greater than the maximum penetration depth of 0.2 foot plus one foot. · The EM61-HH also produced a significant anomaly in the vertical orientation at a depth of 1.5 feet, but the horizontal 14.5mm projectile did not have a significant anomaly deeper than 0.5 foot. · The EM61 and G-858 did not have a significant anomaly for the 14.5mm projectile below 0.5 foot. 35mm Subcaliber · The GEM-3 had significant anomalies in both 35mm subcaliber orientations at its category depth of 2 feet. · The EM61-HH had a significant anomaly for the vertical 35mm subcaliber at a depth of 2 feet, but only for a horizontal 35mm down to 1.5 feet. · The EM61 and G-858 did not have significant anomalies for the 35mm subcaliber deeper than 1 foot. Unlike most of the other items, the 35mm subcaliber consistently resulted in negative vertical magnetic gradient anomalies for the G-858.

2-15 ODDS REPORT

Table 2-9 Static Test OE Category/Group Summary Ordnance Detection and Discrimination Study Fort Ord, California Category Ordnance Item OE Group1 Best Orientation2 Worst Orientation2 EM- EM- EM-61 G-858 61HH GEM-3 EM-61 G-858 61HH GEM-3 II 14.5mm Projectile IIA IIA IIB IIB IIA IIA IIA IIA I MKII Grenade IB IB IB IC IB IB IB IC II 35mm Subcaliber IIA IIA IIB IIC IIA IIA IIA IIB I Signal Illumination Flare IC IB IC IC IC IB IC IC II M9/M11 Grenade IIB IIB IIB IIC IIB IIA IIA IIC II 2.36-inch Rocket IIC IIC IIC IIC IIB IIC IIB IIC V 37mm Projectile VA VA VA VA VA VA VA VA III 22mm Subcaliber IIIA IIIA IIIA IIIA IIIA IIIA IIIA IIIA II 3.5-inch Rocket IIC IIC IIA IIC IIC IIC IIA IIC III 60mm Projectile IIIB IIIB IIIB IIIB IIIA IIIA IIIA IIIB V 75mm Projectile VA VA VA VA VA VA VA VA IV 81mm Projectile IVA IVB IVA IVA IVA IVB IVA IVA IV 81mm Illumination IVA IVB IVA IVA IVA IVB IVA IVA III 90mm Projectile IIIB IIIB IIIB IIIB IIIB IIIB IIIA IIIB IX 105mm Projectile IXA IXA IXA IXA IXA IXA IXA IXA V Stokes Mortar VA VB VA VA VA VB VA VA X3 155mm Projectile XA XA XA XA XA XA XA XA 1 OE Group based on the OE Item Category and Depth of Detection determined from Static Testing. "A" signifies that the OE item was not detected at the maximum depth of penetration plus one foot. "B" signifies the OE item was detected at the maximum depth of penetration plus one foot with a signal response value less than 5X background. "C" signifies the OE item was detected at the maximum depth of penetration plus one foot with a signal response value greater than 5X background. 2 Best and worst orientation signifies the deepest depth of detection for either the vertical or horizontal orientation of the OE item as determined from Static Testing. 3 Maximum depth of penetration for the 155mm projectile is believed to be greater than 10 feet. Note: The only orientations tested were horizontal and vertical due to time constraints on the completion of the ODDS project.

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ODDS REPORT Category Depth 9 EM61 G-858 8 EM61-HH

GEM-3 7

Depth (Feet) 4

2 3 - 17

Stokes Mortar 14.5mm Projectile MKII Grenade 81 Illumination 37mm Projectile 3.5-Inch Rocket 60mm Projectile 75mm Projectile 81mm Projectile 90mm Projectile 35mm Subcaliber M9/M11 Grenade 2.36-Inch Rocket 22mm Subcaliber 105mm Projectile 155mm Projectile Signal Illumination OE Item

Figure 2-1 Maximum Detection Depth for the Static Test OE Items in the BEST Orientations

ODDS REPORT

10 Category Depth

9 EM61 G-858

8 EM61-HH GEM-3 7

5 2 - Depth (Feet) 18 4

Figure 2-2 Maximum Detection Depth for the Static Test OE Items in the WORST Orientations

M9/M11 Grenade · The M9/M11 grenade had significant anomalies detected by the G-858 and GEM-3 sensors at 2 feet deep in both orientations. · At the same depth, the EM61 and EM61-HH had a significant anomaly for the M9/M11 in one of the two orientations tested. · All instruments had significant anomalies for the M9/M11 grenade at 1.5 feet deep, more than a foot deeper than the calculated maximum penetration depth of 0.1 foot. 3.5-inch Rocket · The G-858 had a significant anomaly for the 3.5-inch rocket down to 4 feet with SNRs above 10. · The GEM-3 data contains significant anomalies down to 3 feet in both orientations. · The EM61 also had a significant anomaly for the rocket at 3 feet in the vertical orientation, but only to 2 feet in the horizontal orientation. · The EM61-HH data set contains significant anomalies representing only system noise over the 3.5-inch rocket at 3 feet deep in both orientations. · These instruments can find the 3.5-inch rocket at its category depth of 2 feet. 2.5.2.2 Categories III and IV OE Items The 22mm subcaliber, 60mm projectile, 90mm projectile, 81mm projectile and 81mm illumination round are in Categories III to IV. The three projectiles have significant anomalies at the category depth by one or more of the instruments. The 81mm illumination produced significant anomalies in the horizontal orientation by only one instrument, and in the vertical orientation by no instruments at its category depth. The 22mm subcaliber had no significant anomalies in either orientation by any instrument at its category depth. The following subsections highlight observations from tests on each of the ordnance items in Categories III and IV.

22mm subcaliber · Because of its small size and relatively deep penetration depth, the 22mm subcaliber is one of the most difficult OE items to detect. · Of the four instruments, the GEM-3 had a significant anomaly at the deepest depth, 2 feet below the platform in both orientations. 60mm Projectile · The GEM-3 and G-858 had significant anomalies for the 60mm projectile at both orientations at its category depth of 3 feet.

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· The two EM61 instruments had significant anomalies in the vertical orientation at 3 feet. However, in the horizontal orientation the EM61-HH only had significant anomalies at 1.5 feet and the EM61 had significant anomalies at the deepest level tested, 2 feet. 90mm Projectile · The G-858 exhibited the highest SNR over the 90mm projectile at its category depth, 3 feet. · The EM61 and GEM-3 had significant anomalies over the 90mm projectile in both orientations, while the EM61-HH had significant anomalies in the 90mm in the vertical orientation at 3 feet and in the horizontal orientation at 2 feet. 81mm Projectile · The G-858 also had the highest SNR over the 81mm projectile at its category depth of 4 feet. · The maximum detection depths with significant anomalies for the 81mm projectile for the EM61, EM61-HH and GEM-3 were between 2 and 3 feet. 81mm Illumination · All four instruments had significant anomalies for the 81mm illumination in both orientations at a depth of 3 feet. · The GEM-3 was the only instrument that had significant anomalies in the horizontal orientation at its category depth of 4 feet. · The G-858 was not tested in either orientation at a depth of 4 feet. 2.5.2.3 Category V and Greater OE Items The Static Test used three Category V items, the 37mm projectile, the 75mm projectile, and the Stokes trench mortar. Two other tested items, the 105mm and 155mm projectiles, are Categories IX and X, respectively, and therefore beyond the maximum test depth of this study. For tests conducted at depths of 4 feet and greater it was difficult to determine the signal level because the data profile was only 8 feet long, shorter than the width of the anomaly. The SNR measured for these tests may be reduced because the background level was measured within the anomaly. The following subsections highlight observations from tests on each of the ordnance items in Categories V and greater.

37mm Projectile · As with the 22mm subcaliber, the 37mm projectile’s combination of small size and deep penetration led to all instruments failing to produce significant anomalies at its category depth.

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· The GEM-3 dataset contained significant anomalies over the 37mm at 2 feet (in both orientations), 3 feet shallower than the category depth. · The EM61-HH and G-858 had significant anomalies at 1.5 feet, while the EM61 had significant anomalies at 1 foot. 75mm Projectile · None of the instruments had significant anomalies for the 75mm projectile at its category depth of 5 feet. The G-858 came closest, with significant anomalies over the 75mm projectile at 4 feet in both orientations. · The GEM-3 had significant anomalies for the 75mm at 3 feet while the two EM61 instruments had significant anomalies at 2 feet. · The broad anomaly signature at depths of 5 feet may have reduced the SNR measured for these tests. Stokes Mortar · The G-858 was the only instrument that had significant anomalies for the Stokes Mortar at its 5-foot category depth. · The EM61 and GEM-3 had significant anomalies at 4 feet in the best orientation and 3 feet in the worst orientation. · The EM61-HH had significant anomalies for the Stokes at 3 feet in the best orientation and at 2 feet in the worst orientation. 105mm Projectile

None of the instruments was tested at the category depths for the 105mm projectile because the test stand design did not allow such distances between sensor and target. · The G-858 had significant anomalies for the 105mm at the greatest test depth of 6 feet, with SNRs above 10 in both orientations. · The GEM-3 and EM61 had significant anomalies for the 105mm at 4 feet in both orientations. · The EM61-HH had significant anomalies for the 105mm at 3 feet in the vertical orientation and at 2 feet in the horizontal orientation. · The measured SNRs may be lower than expected because the width of the anomalies exceeded the profile length below 4-foot depths. · As with the 35mm subcaliber, the 105mm projectile also produced negative vertical magnetic gradient anomalies with the G-858.

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155mm Projectile

None of the instruments was tested at the category depths for the 155mm projectile because the test stand design did not allow such distances between sensor and target. · Again, the G-858 had significant anomalies for the 155mm projectile deeper than the other instruments, at the greatest test depth of 7 feet in both orientations. · The EM61 had significant anomalies for the projectile at 6 feet deep in both orientations, while the GEM-3 had significant anomalies at 5 feet and the EM61-HH at 4 feet. · The measured SNRs may be lower than expected because the width of the anomalies exceeded the profile length below 4-foot depths. 2.5.2.4 General Observations This section highlights general observations from the Static Test. · In general, the GEM-3 and EM61-HH performed best at finding the smaller items like the 14.5mm projectile and the MK II grenade. · The G-858 proved to be the best choice for detecting the larger projectiles. · The EM61 also performed well with the medium-sized and larger projectiles. · These tests were conducted in a very controlled environment. (Bringing the instruments down from the test stand onto the seeded or Field Trial Sites increased the instrument noise and added many potential sources of error.) · Most of these items produced positive vertical magnetic gradient anomalies. · The 35mm subcaliber and 105mm projectile consistently produced negative vertical magnetic gradient anomalies. The two test objects may have had remnant magnetic moments that distorted the profiles. 2.5.3 Falloff Curve Analysis

Depth of detection was also evaluated by plotting instrument response falloff curves for each instrument tested in the vertical and horizontal orientation for selected OE items in each category and group. The falloff curves are plotted on a log-linear scale and provide a visual perspective of depth effects on the magnitude of the response signal. Falloff response curves appear in Appendix B Tab 3.

The data from the falloff responses indicate the following: (1) magnetometer response is less effected by depth than the EM instruments; (2) the GEM-3 (FDEM) was less affected by the orientation of the item than the other EM instruments; and (3) the EM61-HH and the GEM-3 had a much higher signal response for the smaller items at the shallow depths than the EM61; however the EM61 could detect the larger items at deeper depths.

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USAESCH OE Center of Expertise geophysical detection criteria for OE were plotted for comparison to the signal response. Figure 2-3 is a typical plot illustrating detection depths for the three EM instruments demonstrated along with the USAESCH detection criteria. In this case, the background for all three instruments is normalized to a value of 1. Values less than 1 indicate that the presence of the item lowered the EM response.

EM61 falloff curves for a variety of OE items were compared to determine any similarities in signal falloff response. The data indicate that the falloff curves are similar and have close to the same slope. These results also suggest that the falloff response for the EM61 can be roughly predicted by a log-linear model; that is, the falloff in the EM response is proportional to the depth of the object and an empirical constant. Figure 2-4 shows the measured and the predicted values for three OE items vertically oriented.

Ft. Ord - ODDS Project - Static Test Peak Response Fall-Off Curve 3" Stokes Trench Mortar, Horizontal

10000

1000 CEHND Detection Requirement.

100

10 Normalized EM Response 1

0.1 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Depth to Top of OE Item EM61 (Feet) EM61HH GEM3

Figure 2-3 Normalized EM Response for Three EM Detectors Used to Detect a Horizontally Oriented Stokes Mortar. (Background response in air is equal to 1 and the required CEHNC detection depth is shown as a vertical line.) The predicted values were determined using a simple log-linear signal falloff model as follows. FcD RN = R0*10 where RN = normalized signal response R0 = signal response at initial depth Fc = empirical determined falloff constant for EM instrument

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D = depth of buried item This analysis indicates that the simplistic log linear model predicts fairly well the expected EM response at higher signal responses but as the peak values approach the noise levels of the instrument the model may underestimate the measured peak value. Similar results were obtained for the EM61 with the OE items oriented horizontally. Figure 2-5 illustrates the predictive peak response values versus the actual measured

Ft. Ord - ODDS Project - Static Test EM61 Peak Response Fall-Off Curve Vertical Orientated OE Items

EM61 60mm 1000 EM61 81mm EM61 105mm Predicted 60mm Predicted 81mm Predicted 105mm 100

10 EM Response

1 0.5 1 1.5 2 2.5 3 Depth to Top of OE Item (Feet)

Figure 2-4 Measured EM61 Signal Response and Predicted Response for Three Vertically Oriented OE Items at Various Depths

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Ft. Ord - ODDS Project - Static "Free Air" Test EM61 Peak Response Fall-Off Curve Horizontal Orientated OE Items

EM61 60mm 1000 EM61 81mm EM61 105mm Predicted 60mm Predicted 81mm Predicted 105mm 100

10 EM Response

1 0.5 1 1.5 2 2.5 Depth to Top of OE Item (Feet)

Figure 2-5 Measured EM61 Signal Response and Predicted Response for Three Horizontally Oriented OE Items at Various Depths values. In both the vertical and horizontal orientations the empirical drop-off constant used in the analysis was the same and was calculated at a value of –0.66.

2.6 STATIC TEST SUMMARY

Data collected during the ODDS Static Test help to better understand the expected signal responses for typical OE items at Fort Ord. OE groups were developed and used in developing the seeding strategy for the second phase of the ODDS.

The free-air tests resulted in a much better understanding of what instrument responses should look like in the best circumstances. The following sections make clear that rough ground and vegetation severely inhibit and reduce the ability of these sensitive tools to detect, let alone discriminate, buried OE.

However, these results do allow survey designers and others to determine what can be expected in basic detection for an instrument for each OE. The profiles compiled here form the basis of the Fort Ord OE geophysical signature library.

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