701 TFJD590-07-175137 May 25, 2006 13:58

A Metal Detector Study to Locate Inactive SmallArms Range Impact Areas

KYMBERLY C. TAKASAKI,a W. ANDY MARTIN,b

VICTOR F. MEDINA,c AND JOSEPH R. MARSHa

aU.S. Army Corps of Engineers, Seattle District, Seattle, WA, USAbApplied Research Associates, Inc., Vicksburg, MS, USAcU.S. Army Engineer Research and Development Center—Environmental Lab,Vicksburg, MS, USA

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701 TFJD590-07-175137 May 25, 2006 13:58

Soil & Sediment Contamination, 15:1–8, 2006Copyright © Taylor & Francis Group, LLCISSN: 1532-0383 print / 1549-7887 onlineDOI: 10.1080/15320380600751744

A Metal Detector Study to Locate Inactive SmallArms Range Impact Areas

KYMBERLY C. TAKASAKI,a W. ANDY MARTIN,b

VICTOR F. MEDINA,c AND JOSEPH R. MARSHa

aU.S. Army Corps of Engineers, Seattle District, Seattle, WA, USAbApplied Research Associates, Inc., Vicksburg, MS, USAcU.S. Army Engineer Research and Development Center—Environmental Lab,Vicksburg, MS, USA

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Historical records suggested the existence of .45 caliber Thompson sub-machine gunranges near the Fort Lewis Evergreen Range; however, the precise location of the bullet10impact area was not known. The site covered 20 acres, too large to cost-effectivelycharacterize using convention grid sampling techniques. As an alternative, a study wasconducted using a hand-held metal detector to locate the bullet impact areas.

The metal detector chosen, a Garrett Graphic Target ImagingTM (GTI) 2500, hasan LCD screen, which provides the user information on the potential size and depth of15the object causing the signal. A two-man team performed the study and bullet detectionwas confirmed by excavation.

The metal detector proved effective at finding .45 caliber bullets. Three impactareas were successfully identified and marked using a global positioning system (GPS).The metal detecting strategy saved substantial sampling time and over $35,000.00 by20decreasing the sampling area by 93 percent.

Keywords Lead, metal detection, small arms firing range, bullets

Introduction

There are over 3,000 active Department of Defense (DoD) small arms firing ranges (SAFRs)currently in use, and it is estimated that over 2 million pounds of lead are expended every25year at these ranges (ITRC, 2003). The DoD is managing a further 200 ranges in variousstatus of closure (ITRC, 2003). Due to incomplete record keeping in the past, it is likelythat there are substantial numbers of undocumented ranges that are no longer active.

Depending on the velocity of the bullet projectiles and the impact berm material, bul-lets can penetrate into the ground as whole projectiles, fragment upon impact into smaller30pieces, or smear onto pieces of berm material. These small bullet fragments can be in-troduced into the surrounding environment through groundwater, surface water, and wind

We would like to give special thanks to some people that assisted with the work on this project.Mr. Richard Wilson of the Department of Public Works at Fort Lewis, WA, for supporting the use ofmetal detectors for the study. Mr. Chris Foote, CSC, Vicksburg, MS, for taking the time to train us onthe metal detector. The project was funded by the Seattle District of the United States Army Corps ofEngineers.

Address correspondence to W. Andy Martin, Applied Research Associates, Inc., 119 MonumentPlace, Vicksburg, MS 39180, USA. E-mail: andy.martin@ara.com

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transport. Cao et al. (2003a) studied five SAFRs in Florida, and found elevated lead lev-els in berm soils, in nearby surface water, and in plant material. In another study, Caoet al. (2003b) found that most soils from impact berms from two shooting ranges failed the 35synthetic precipitation leaching procedure, which simulates leaching from rainfall. Craiget al. (1999) documented off-site migration of lead due to surface water erosion at a firingrange in Virginia. A study of shooting ranges in Sweden found elevated lead levels in soils(Lin et al., 1995). Analysis of toxicity characteristic leaching procedure extractions of ri-fle/shooting range soils indicated that most exceed the 5 mg L−1 level that the Resource 40Conservation and Recovery Act defines a waste as hazardous (Chen et al., 2002). A studyof small arms ranges in Ontario, Canada, indicated that about 10% of the ranges had soilcharacteristics that promote lead corrosion and migration (Darling and Thomas, 2003).These indicate that closed ranges must be managed to prevent lead exposures to nearbypopulations. 45

Best management practices have been established for closed SAFRs, including stabi-lization of the lead and reuse, soil washing technologies, and physical separation of largelead fragments (ITRC, 2003; USEPA, 2003). But the most reliable approach is the removalof the lead source from the range (USEPA, 2003).

In order for cost-effective treatment or removal to occur, the range impact areas must 50be delineated. Unfortunately, the precise locations of older firing ranges at some militaryinstallations are often unknown, because the training and land management records arevague or have been destroyed. As time passes, the training requirements for soldiers canchange dramatically, resulting in multiple adaptations in land use. The demands of wartimetraining further necessitate changes in land use at training facilities, which often has resulted 55in poor documentation of changes.

Precisely locating an abandoned, unmarked range can be expensive and challenging.The area of interest is generally marked in a grid pattern, and samples are collected andanalyzed, often at great expense. The bullets are usually clumped around target areas, creat-ing extreme heterogeneity of impact areas, which requires intensive sampling to delineate, 60as clumped distributions are particularly challenging to appropriately obtain representativesamples for (Bros and Cowell, 1987).

Fort Lewis in Western Washington State, which is in the northwestern portion of thecontinental United States, is a military base that has undergone dramatic changes over itshistory. Fort Lewis was established in 1916 and expanded from 62,000 to 86,000 acres during 65the Second World War (Fort Lewis, 2000). This resulted in the cantonment area (the areaof the base where soldiers and base personnel live and conduct daily business) overrunninga number of older training ranges. These changes occurred rapidly, and record keeping didnot adequately provide an accurate account of the exact locations of the older ranges.

An example of this has occurred at the Evergreen Range, an older training area located 70at Fort Lewis. The Evergreen Range consists of an obvious berm where firing of .30 calibermachine guns was conducted as part of infiltration training. In addition, there were reportsof .45 caliber Thompson sub-machine gun training ranges in the area. The Thompson sub-machine gun range was last used more than 50 years ago and the range impact area was notknown. No obvious impact berms or bullet trenches could be recognized. The Evergreen 75Range and its surrounding areas were zoned for future construction projects. Therefore,it was necessary to conduct a site characterization to locate and evaluate the old impactarea. Conventional sampling methods, which involve collecting samples and analyzingthem (whether in a laboratory or by field X-ray fluorescence) in a grid pattern, would beexpensive and time-consuming in order to locate the Thompson sub-machine gun impact 80area, as the potential sampling area was 20 acres.

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A Metal Detector Study to Locate Inactive Small Arms Range Impact Areas 3

Metal detection has been used to find antipersonnel mines (Bruschini et al., 1998), as

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well as to locate drummed hazardous wastes in an uncontrolled landfill (Lord and Koerner,1988). It also has been effectively used to find metallic artifacts, including bullets and othermunitions, in archaeological investigations (Bell, 2004; Bauer and Rogge, 1998; Geier and85Potter, 2000; Hesse, 1999; Marmor, 1997; McBride and Stottman, 2000; Roach, 2001). Weused the Garrett GTI 2500 metal detector to locate the impact area of the old Thompsonsub-machine gun range. This paper summarizes the study and documents the effectivenessof this approach.

Methods90

Site Background

The Evergreen Range (Figure 1) was part of a WW II range complex that contained aninfiltration course, which was readily identified by a large impact berm. In addition, areview of historical documents indicated the existence of a Thompson sub-machine gunrange in the 20-acre site, but the precise location was not known. The range impact area95was overgrown with tall trees and brush on gently rolling hills, adjacent to an old landfill.The area was also surrounded by asphalt roads on all sides and had gravel and dirt roadsthat are currently used by soldiers for day-to-day training.

Figure 1. The Thompson sub-machine gun range at Fort Lewis, WA, with survey area, area coveredby the metal detector team and impact areas identified by circles in upper center of figure.

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4 K. C. Takasaki et al.

Site visits did not indicate any visual features, such as berms, bullets or trenches,signifying range use. The site has been overgrown with vegetation covering all traces of 100bullets, bullet pockets, or range activity. Review of historical records did not indicate anytraining with explosive munitions. Physical sampling was considered, but since the exactlocation of the submachine gun impact area was not known, and the size of the area was quitelarge (20 acres), the cost and time involved was too great. Consequently, characterizationusing a hand-held metal detector was conducted. 105

Metal Detection

Modern metal detection equipment has evolved incorporating discriminators and sensorsthat allow the user to determine the approximate depth, size, and potential identity of anobject before digging it up. Based on a review of features and price, the Garrett (Garrett MetalDetectors, Garland, TX) GTI 2500 metal detector was selected for this study. In general, 110the GTI 2500 transmits a specific electro-magnetic frequency; an object in the ground willemit a different ground wave frequency that is then detected. The metal detector providesboth visual, via an LCD screen, and audio signals for interpretation by the user. Prior toconducting the fieldwork we practiced with the GTI 2500 for about six hours and were ableto determine the appropriate signals of bullets that were similar to the .45 caliber bullets we 115wanted to locate at the field site.

The LCD screen of the GTI 2500 provides the approximate size, depth and potentialidentity of an object (Figure 2). By understanding the characteristics of the desired objectslike the .45 caliber bullets and practicing on such objects the operator can determine withsome certainty what an object, is, but excavation of the object is necessary for positive 120identification.

The .45 caliber bullet that was used by the Thompson sub-machine gun has changedlittle since its introduction in 1911 (Mattioli, 2004). It contains a lead slug that is encasedin a copper-nickel metal jacket, with a weight of 230 grains (14.9 grams) and a length of1.73 centimeters. With the introduction of assault rifles during the 1960s, sub-machine guns 125like the Thompson were phased out of use in the military. Today’s 5.56 mm M16 round isa lead alloy containing a steel penetrator, with a weight of 63 grains (4.08 grams) and is2.3 centimeters long (FAS, 1998).

Field Methods

The field study was completed using a two-person team, each with specific roles. One 130member of the team laid out a transect and mapped locations using a GPS, while theother team member operated the metal detector, confirmed detections by excavation, andcollected samples. At the field site a grid pattern was established by marking the startpoint and endpoints of north-south transects with a GPS. Transect lines were laid out on a10-ft spacing grid. However, as the fieldwork proceeded, a wider spacing of 50 ft proved 135sufficient to cover the area, because the metal detector operator was able to cover wideside to side swatches during his transect. A compass was used to stay on the north-southtransects through thick vegetation and overgrown trees. The transect lines were marked withsurveyors’ tape for the metal detector operator to follow.

If the metal detector gave a signal that was potentially caused by a bullet, the oper- 140ator carefully studied the area with the metal detector to precisely determine the sourcelocation. Then, the target area was excavated in order to confirm if the signal was, indeed,from a bullet source. The metal detector operator marked the bullet sites, which were then

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A Metal Detector Study to Locate Inactive Small Arms Range Impact Areas 5

Figure 2. (a) LCD screen and button controls of the GTI 2500. (b) Schematic of screen indicating howit provides information that allows user to discriminate various signals by depicting the approximatesize, depth, and potential identity of objects.

logged and mapped by the GPS operator. Only those locations positively correlated to re-covered bullets were mapped. The total area covered in a four-day period was approximately14520 acres.

Results

Detection of Bullets

A dense, intact bullet gave a distinct signal on the metal detector. As a bullet corrodesor oxidizes, the released metal spreads into the surrounding soil, creating a halo effect,150which changed the metal detector signals. With experience, the metal detector operator wasable to identify both intact bullets and corroded bullets (with halo effects). Other metalobjects found at the site included expended signal flares and metal cans, which were easily

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6 K. C. Takasaki et al.

discriminated by interpreting the signals on the metal detector. However, expended brassfrom blank training ammunition and 5.56 mm rounds, both of which were present at the 155site, produced similar signals to the .45 caliber bullets. Therefore, the only way to positivelyidentify the .45 caliber round was to carefully dig up the round. The majority of the .45caliber bullets were retrieved 4-6 inches below the ground surface.

Impact Areas

Once a bullet location was identified, other bullets were found in the general vicinity, as 160would be expected in an impact area. By estimating probable bullet trajectories, we werealso able to focus our metal detecting to find other bullets. Three distinct impact areas ofthe Thompson sub-machine gun range were identified (Figure 1). In addition to .45 caliberbullets, these areas contained expended flare rounds, expended brass from blank trainingammunition, and surprisingly, 5.56 mm bullets. The 5.56 mm bullets are presumably from 165firing M16 rifles, a more modern weapon, indicating more recent use of the area for liveammunition training than previously thought.

Discussion

Poor documentation along with the overgrowth of old training areas decreases the ability toprecisely locate old impact zones. This study documents a successful application for metal 170detection technology for conducting site characterization of the old Thompson sub-machinegun range impact area.

This study reveals lessons that should be employed by other groups wishing to usemetal detectors for small arms range delineation. First, a high quality metal detector shouldbe chosen for these studies. The Garrett GTI 2500 is a top of the line instrument, and 175costs 10 to 20 times more than detectors commonly purchased by casual hobbyists. It isextremely sensitive, but perhaps more important, it has visual screen features coupled withaudio signals that provide an experienced operator with the necessary information to screenout signals that are not likely to be bullets. In addition, the detector has several discriminatormodes that can be used to tune out background iron content in soils, although this feature 180was not needed for this study.

A second lesson is that operator experience was an important factor. As mentioned inthe Methods section, we had a training session prior to going out in the field. Our operatorunderwent detection exercises for over six hours under the guidance of an experiencedmetal detector user. This session allowed the operator to perfect signal identification and 185detection of sources. The instrument is not particularly difficult to use, and it is likely thatmost users could operate it satisfactorily after some initial training. However, it would not beadvisable for an inexperienced user to take an instrument into the field with the expectationof immediately obtaining valid results.

The metal detector study offered two advantages: time and cost savings. Time was a 190critical factor in choosing the metal detector approach. The study covered a 20-acre site in4 days and delineated three impact areas within the site. Traditional sampling would likelytake at least as long, but would require a larger crew to cover the area. Additional timewould have to be taken to allow for analysis of the results. So the metal detection approachsaved time, on the order of two to three weeks. 195

The metal detector study also saved money. Table 1 summarizes cost estimates for themetal detector study as compared to a conventional sampling strategy. The metal detectorapproach was estimated to cost less than half of the conventional approach.

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A Metal Detector Study to Locate Inactive Small Arms Range Impact Areas 7

Table 1Comparison of estimated cost savings by A) metal detector work to locate thesampling target areas in 20 acres, then sampling of those focused areas, and B)

sampling all 20 acres

A) Metal DetectorSurvey and Sampling of B) Grid Sampling of

Activity Impact Areas 20-Acre Site

Area to be Sampled (ft2) 59,538 870,537Number of Sample Locations

(50 ft. Grid)24 349

People 2 2Hours per Sample Location 1 1Metal Detector Survey $16,000.00 N/ALabor Costs (per hour) $65.00 $65.00Sampling Costs $3,120.00 $45,326.67Cost per sample (per sample) $30.00 $30.00Lab Costs $720.00 $10,460.00Total Costs $19,840.00 $55,786.67

In conclusion, a metal detector was used to delineate three impact areas for old .45caliber Thompson sub-machine gun range. The study was conducted quickly and at a muchlower cost than traditional sampling methods. The approach is adaptable to other ranges.200

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