Cross-Hole Radar Scanning of Two Vertical, 

Permeable, Reactive-Iron Walls at the Massachusetts 

Military Reservation, Cape Cod, Massachusetts

Water-Resources Investigations Report 00-4145

Prepared in cooperation with the Air Force Center for Environmental Excellence

U.S. Department of the Interior

U.S. Geological Survey
Cover: A 250-megahertz borehole-radar antenna at the Massachusetts Military Reservation, 

Cape Cod, Massachusetts.
U.S. Department of the Interior

U.S. Geological Survey

Cross-Hole Radar Scanning of Two Vertical, 

Permeable, Reactive-Iron Walls at the Massachusetts 

Military Reservation, Cape Cod, Massachusetts

By John W. Lane Jr., Peter K. Joesten, and Jennifer G. Savoie

Water-Resources Investigation Report 00-4145

Prepared in cooperation with the Air Force Center for Environmental Excellence

Storrs, Connecticut

2001
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of fi rm, trade, and brand names in this report is for identifi cation purposes only and 

does not constitute endorsement by the U.S. Geological Survey.

For additional information write to:

Branch Chief

U.S. Geological Survey

11 Sherman Place, U-5015

Storrs, CT 06269

http://water.usgs.gov/ogw/bgas

Copies of this report can be purchased from:

U.S. Geological Survey

Branch of Information Services

Box 25286, Federal Center

Denver, CO 80225

http://www.usgs.gov
CONTENTS

Abstract......................................................................................................................................................... 1

Introduction.................................................................................................................................................. 2

Numerical and Physical Modeling of Vertical, Permeable, Zero-Valent, Reactive-Iron Walls...................... 4

 Numerical Modeling......................................................................................................................... 4

 Physical Modeling............................................................................................................................ 8

Collection, Processing, and Analysis of Geophysical Data......................................................................... 11

 Electromagnetic Induction.............................................................................................................. 11

 Borehole Deviation......................................................................................................................... 13

 Cross-Hole Radar Scanning............................................................................................................ 13

Summary..................................................................................................................................................... 16

References Cited......................................................................................................................................... 17

FIGURES

1. Map showing location of the study area and the CS-10 plume, Massachusetts Military

 Reservation, Cape Cod, Mass............................................................................................................ 2

2. Conceptual diagram of contaminated ground water passing through a zero-valent reactive-iron

 wall.................................................................................................................................................. 3

3. Conceptual diagram showing the effects of iron distribution and discontinuities on the 

 transmission of radar waves......................................................................................................... 4

4. Diagram of the two-dimensional fi nite-difference time-domain numerical model used for this

 study................................................................................................................................................ 5

5. Graph showing waveform characteristics of the 250-megahertz Ricker wavelet used for the

 numerical modeling and a 250-megahertz transmitted radar wave from the fi eld data...................... 5

6. Diagram of the two-dimensional fi nite-difference time-domain numerical model geometry 

 used to determine the effects of wall edges on radar transmission characteristics............................. 6

7. Diagram of the two-dimensional fi nite-difference time-domain numerical model geometry

 used to determine the effects of wall discontinuities (holes) on radar transmission

 characteristics.................................................................................................................................. 6

8. Plot of two-dimensional fi nite-difference time-domain numerical model radar-pulse amplitude 

 results normalized to background amplitudes................................................................................... 7

9. Plot of two-dimensional fi nite-difference time-domain numerical radar-waveform results 

 plotted as a function of time............................................................................................................... 7

10. Graph of two-dimensional fi nite-difference time-domain numerical model results showing

 normalized maximum peak-to-peak amplitude plotted against hole aperture................................... 8

11. Photograph of the physical model assembly with the perfect-conductor analog extending half

 of the length of the tank..................................................................................................................... 9

12. Conceptual diagram of the physical model assembly consisting of a tank fi lled with 

 saturated sand and a perfect-conductor analog extending the length of the tank................................ 9

Contents III
13. Conceptual diagram of the physical model assembly with a perfect-conductor analog 

 extending half of the length of the tank............................................................................................. 9

14. Conceptual diagram of the physical model assembly containing a perfect-conductor analog

 with holes of apertures 0.36 and 2.00 wavelengths............................................................................ 9

15. Plot of a waveform transmitted through the background physical model and a waveform

 transmitted through the perfect-conductor analog.......................................................................... 10

16. Plot of radar data from the half-wall physical model overlain with results from the half-wall

 numerical model............................................................................................................................. 11

17. Plot of normalized peak-to-peak amplitudes for waves transmitted in the physical model 

 through the perfect-conductor analog for holes of 0.36 and 2.00 wavelengths ............................... 11

18. Map view of the study area showing observation boreholes and transmission raypaths, 

 Massachusetts Military Reservation, Cape Cod, Mass................................................................... 12

19. Graph of borehole electromagnetic logging of boreholes north of the A-wall after the A-wall 

 installation, Massachusetts Military Reservation, Cape Cod, Mass................................................ 12

20. Plot of pre-injection direct-wave amplitudes across the B-wall, Massachusetts Military 

 Reservation, Cape Cod, Mass......................................................................................................... 13

21. Plot of post-injection direct-wave amplitudes across the A-wall, Massachusetts Military

 Reservation, Cape Cod, Mass......................................................................................................... 14

22. Plot of post-injection direct-wave amplitudes across the B-wall, Massachusetts Military

 Reservation, Cape Cod, Mass......................................................................................................... 14

23. Map view of the study area showing observation boreholes and transmission raypaths lost due

 to damaged boreholes, Massachusetts Military Reservation, Cape Cod, Mass............................... 14

24. Plot of normalized model-wall amplitudes for a 3.10-meter wall and the normalized

fi eld-data amplitudes from the common-depth radar survey between boreholes RW-20 

 and RW-13, Massachusetts Military Reservation, Cape Cod, Mass................................................ 15

25. Plot of post-injection direct-wave amplitudes across the A-wall showing normalized 

 amplitudes of less than 0.43, Massachusetts Military Reservation, Cape Cod, Mass...................... 15

26. Plot of post-injection direct-wave amplitudes across the B-wall showing normalized

 amplitudes of less than 0.43, Massachusetts Military Reservation, Cape Cod, Mass...................... 15

CONVERSION FACTORS AND ABBREVIATIONS

 By To obtain

 0.3937 inch (in)

 3.281 foot (ft)

 

Other abbreviations used in this report:

mV, microvolt

MHz, megahertz

S/m, siemens per meter

IV Contents

Multiply 

centimeter (cm)

meter (m)
Cross-Hole Radar Scanning of Two Vertical, 

Permeable, Reactive-Iron Walls at the Massachusetts 

Military Reservation, Cape Cod, Massachusetts

By John W. Lane Jr., Peter K. Joesten, and Jennifer G. Savoie

ABSTRACT

 A pilot-scale study was conducted by 

the U.S. Army National Guard (USANG) at the 

Massachusetts Military Reservation (MMR) on 

Cape Cod, Massachusetts, to assess the use of 

a hydraulic-fracturing method to create vertical, 

permeable walls of zero-valent iron to passively 

remediate ground water contaminated with chlorinated solvents. The study was conducted near 

the source area of the Chemical Spill-10 (CS-10) 

plume, a plume containing chlorinated solvents 

that underlies the MMR. Ground-water contamination near the source area extends from about 

24 m (meters) to 35 m below land surface. The 

USANG designed two reactive-iron walls to be 

12 m long and positioned 24 to 37 m below 

land surface to intersect and remediate part of the 

CS-10 plume.

 Because iron, as an electrical conductor, 

absorbs electromagnetic energy, the U.S. Geological Survey used a cross-hole common-depth, 

radar scanning method to assess the continuity 

and to estimate the lateral and vertical extent of 

the two reactive-iron walls. The cross-hole radar 

surveys were conducted in boreholes on opposite 

sides of the iron injection zones using electricdipole antennas with dominant center frequencies 

of 100 and 250 MHz. Signifi cant decreases in 

the radar-pulse amplitudes observed in scans that 

traversed the injection zones were interpreted by 

comparing fi eld data to results of two-dimensional fi nite-difference time-domain numerical 

models and laboratory-scale physical models.

 The numerical and physical models simulate a wall of perfectly conducting material 

embedded in saturated sand. Results from the 

numerical and physical models show that the 

amplitude of the radar pulse transmitted across 

the edge of a conductive wall is about 43 percent 

of the amplitude of a radar pulse transmitted 

across background material. The amplitude of 

a radar pulse transmitted through a hole in a 

conductive wall increases as the aperture of the 

hole increases. The modeling results indicate 

that holes with an aperture of less than 40 percent 

of the dominant wavelength of the radar pulse are 

not likely to be detected.

 Based on the results of the numerical 

and physical modeling, the decreases in radarpulse amplitudes observed in scans traversing 

the injection zones are interpreted as electrically 

conductive zones that outline the distribution of 

iron. The area interpreted as iron in the northern 

A-wall contains two zones -- an upper zone about 

10 m wide, extending from about 25 to 31 m 

below land surface, and a lower zone about 8 

m wide, extending from 31.5 to 34.5 m below 

land surface. The area interpreted as iron in the 

southern B-wall is about 9 m wide, extending 

from about 27 to 34.5 m below land surface. No 

discrete holes were interpreted in either the A- or 

B-wall zones. 

ABSTRACT 1
 The interpretation of the fi eld data suggests that (1) the hydraulic-fracturing method 

introduced iron into the subsurface, but not in 

the dimensions originally proposed; (2) the iron 

within the treatment zones is distributed in a generally continuous manner; and (3) excluding the 

discontinuity in the A-wall, holes within the iron 

treatment zone, if any, exist at scales smaller than 

about 10 cm, the resolution limit of the radar 

antennas and acquisition geometry used for this 

study. The cross-hole radar method appears to 

have been an effective method for delineating the 

distribution of iron in the two walls; however, 

the veracity of the results cannot be ascertained 

without excavation or drilling into the treatment 

zone.

INTRODUCTION

 Ground water beneath and downgradient 

from the Massachusetts Military Reservation (MMR), 

on Cape Cod, Massachusetts, has been affected by 

contaminants used during past decades of military 

operations (Savoie and LeBlanc, 1998). Chlorinated 

solvents that have entered the ground-water system 

are moving away from the MMR in the underlying 

sand-and-gravel aquifer toward streams, ponds, and 

coastal bays. Chemical Spill-10 (CS-10) is a 

chlorinated-solvent plume that emanates from a site 

used from 1960 to 1973 by the U.S. Air Force to 

house and maintain the Boeing Michigan Aerospace 

Research Center (BOMARC) ground-to-air missiles 

and launcher systems (fi g. 1) (ABB Environmental 

Services, Inc., 1993). From 1978 to the present, the 

site has been used by the U.S. Army National 

Guard to store and maintain armored and military 

vehicles. Primary sources of contamination were 

caused by chemical spills and from the disposal of 

2 Cross-Hole Radar Scanning of Two Vertical, Permeable, Reactive-Iron Walls at the Massachusetts Military Reservation, Cape

Cod, Massachusetts

Figure 1. Location of the study area and the CS-10 plume, Massachusetts Military Reservation, Cape Cod, Mass.
chemical wastes in leaching wells and oil interceptors 

(ABB Environmental Services, Inc., 1993). The 

contaminants in the ground water of greatest concern 

include trichloroethene (TCE) and tetrachloroethene 

(PCE) (ABB Environmental Services, Inc., 1993).

 To prevent continued spread of these chemicals from the source area, the MMR Installation Restoration Program contracted with the University of 

Waterloo to design and manage the installation of 

a pilot-scale permeable zero-valent iron remediation 

system in the path of the plume downgradient from 

the source area. Zero-valent iron has been used 

to remediate ground water contaminated with chlorinated solvents at several sites in North America and 

Europe (Gillham and O’Hannesin, 1994). Permeable 

walls of zero-valent iron can provide a relatively inexpensive alternative to pump-and-treat technology. The 

method does not require the withdrawal of ground 

water, thus minimizing changes to ambient water 

levels and natural ground-water fl ow. At many of 

these sites, a funnel-and-gate system has been implemented (Starr and Cherry, 1994; Smyth and others, 

1996). In this system, an impermeable barrier, which 

often consists of sheet pilings, channels ground water 

towards a gate, which is fi lled with zero-valent granular iron fi lings. As contaminated ground water moves 

through the treatment zone, chlorinated solvents are 

reductively dechlorinated to less harmful chemicals 

(Gillham and O’Hannesin, 1994). 

 The CS-10 plume at the former BOMARC 

site is 24 to 37 m below land surface. Because 

these depths exceed the practical limit for the funneland-gate method, an alternative installation method 

was required to use zero-valent iron to remediate the 

CS-10 plume. The installation method selected for 

the CS-10 plume was hydraulic fracturing (Hubble 

and Gillham, 1997, 1999; Hubble and others, 1997). 

The hydraulic fracturing uses a proprietary injection 

technology to install permeable zero-valent reactiveiron walls in unconsolidated sediments (Grant 

Hocking and S.L. Wells, Golder Sierra LLC, written 

commun., 1997). 

 In 1998, a pilot-scale test of the hydraulicfracturing installation method was conducted near the 

source area of the CS-10 plume. Two parallel, vertical iron walls (fi g. 1) were emplaced to intersect contaminated ground water from 24 to 37 m below land 

surface. The pilot-scale test was designed to demonstrate the application of the in-place remediation technology and the vertical hydraulic-fracturing method 

of installation. The CS-10 plume posed a particular 

challenge for vertical wall installation because the 

site, on a glacial outwash plain composed of interbedded sand and gravel, has a 24-m-thick unsaturated 

zone. The depth of the installation prevented physical 

inspection of the walls; therefore a remote-sensing 

method was required to determine the boundaries and 

continuity of the walls.

 The U.S. Geological Survey (USGS), in 

cooperation with the U.S. Air Force Center for 

Environmental Excellence, conducted a study using 

cross-hole common-depth (CD) radar scanning as a 

remote-sensing method to determine the lateral and 

vertical extent of the iron walls and to determine 

whether large holes were present in the iron walls 

that could allow contaminated ground water to pass 

untreated through the remediation zone (fi g. 2). The 

cross-hole radar method was chosen because a radar 

pulse can be signifi cantly absorbed by accumulations 

of iron particles between a radar transmitter and 

receiver (fi g. 3). To constrain the estimates of wall 

boundaries and continuity, the effect of wall edges 

and holes on the cross-hole radar data was predicted 

through numerical and physical modeling. In this 

report, the results of numerical and physical modeling 

are presented, and the cross-hole radar fi eld data are 

interpreted to estimate the vertical and lateral distribution and continuity of two vertical, permeable, zerovalent iron walls installed near the source area of the 

CS-10 plume at the MMR. 

INTRODUCTION 3

Figure 2. Conceptual diagram of contaminated ground 

water passing through a zero-valent reactive-iron wall.
 The authors thank the U.S. Air Force Center 

for Environmental Excellence at the Massachusetts 

Military Reservation, Cape Cod, Mass., Edward 

L. Pesce, Rose Forbes, Michael Minior, and the 

U.S. Army National Guard for their support. The 

authors gratefully acknowledge David Hubble of the 

University of Waterloo for his assistance, Lei Xiao 

and Dr. Lanbo Liu of the University of Connecticut 

for the use of the fi nite-difference numerical model, 

and Dr. Roelof Versteeg and Justin Kuczynski of 

the Aldridge Geophysical Imaging Laboratory at 

Columbia University for their assistance with the 

physical modeling.

NUMERICAL AND PHYSICAL MODELING 

OF VERTICAL, PERMEABLE, ZEROVALENT, REACTIVE-IRON WALLS

 Conventional radar tomography methods use 

the travel-time or amplitude of the directly transmitted 

radar pulse acquired from many different transmitterreceiver pairs to generate a model of subsurface 

properties, such as velocity or attenuation, that 

can be interpreted as images. For this study, 

the wall-construction materials and verticalemplacement geometry imposed constraints on the 

use of conventional tomographic-imaging methods. 

Because the iron used in the construction of 

the walls absorbs radar waves, large regions of 

the iron injection zones were expected to act as 

perfect conductors that would completely block 

directly transmitted radar pulses. Perfect conductors 

are opaque to the radar, and as a result, many 

measurements needed for tomographic imaging are 

unavailable, which in turn degrades the quality, 

resolution, and uniqueness of tomograms produced 

from the cross-hole radar data. 

 Instead of using conventional tomographicimage reconstruction methods, radar fi eld data were 

analyzed by using the results of numerical and physical models developed to predict the effects of wall 

edges and holes on CD cross-hole radar measurements. The use of the perfect conductor conceptual 

model reduces the imaging problem to the identifi cation of (1) conductor edges and (2) holes in 

the conductor. This simplifi es cross-hole radar data 

acquisition by limiting measurements to horizontal 

scans acquired from radar transmitters and receivers 

located at common depths. 

Numerical Modeling

 For this study, the effect of wall edges and 

holes on CD cross-hole radar amplitudes was determined using a two-dimensional fi nite-difference timedomain (2D FDTD) model developed by Xiao and 

others (1998). The fi nite-difference grid for the 

numerical models contained 5- by 5-cm cells, and the 

model domain extended 12.8 m (256 cells) in both 

the horizontal and vertical directions (fi g. 4). The 

outer 2.5 m (50 cells) of the model domain is a superabsorbing boundary, designed to minimize spurious 

model-boundary refl ection effects (Xiao and others, 

1998). The electromagnetic properties of simulated 

materials in the model domain were chosen to be consistent with fi eld measurements at the site. The model 

simulated a saturated sand with a relative dielectric 

permittivity (εr) of 25, an electrical conductivity (σ) 

of 0.01 S/m, and a relative magnetic permeability 

(μr) of 1.00 (Lane and others, 1999). Because the 

electrical conductivity of iron is so high (1 x 107 S/m) 

(Carmichael, 1989), the model wall was approximated 

as a near-perfect conductor, with a thickness of 10 

cm. 

Figure 3. Conceptual diagram showing the effects of iron 

distribution and discontinuities on the transmission of radar 

waves.

4 Cross-Hole Radar Scanning of Two Vertical, Permeable, Reactive-Iron Walls at the Massachusetts Military Reservation, Cape

Cod, Massachusetts
Transmitters Receivers

SATURATED SAND

Relative dielectric permittivity= 25

Electrical conductivity = 

0.01 siemens/meter

SUPER-ABSORBING

BOUNDARY

12.8 meters (256 cells)

12.8 meters

(256 cells)

2.5 meters

(50 cells)

Figure 4. The two-dimensional fi nite-difference timedomain numerical model used for this study. [The model 

extends 12.8 meters (256 cells) in the vertical direction and 

12.8 meters (256 cells) in the horizontal direction. There 

is a 2.5-meter (50 cell) super-absorbing boundary on the 

model to minimize edge effects (Xiao and others, 1998).]

 The cross-hole radar pulse was simulated 

using a Ricker wavelet (Ricker, 1953) with a center 

frequency of 250-MHz. The pulse had a wavelength 

in saturated sand of about 24 cm. The frequency 

of the simulated radar pulse was chosen to approximate the center frequency of the borehole radar antennas used for the fi eld study. The Ricker wavelet 

was selected for the numerical modeling because the 

shape of this wavelet approximates the waveform produced by the radar antennas used for the fi eld study 

(fi g. 5). Time-domain waveforms produced by the 

numerical models were sampled at 5,270 MHz using 

1,024 samples per waveform. This sampling rate 

was selected to ensure that the frequency components 

within the radar-pulse frequency band were properly 

recorded.

 A model that contained a 10-cm thick vertical 

wall extending from the center of the model domain 

to the model boundary (fi g. 6) was used to determine 

the effect of wall edges on the directly transmitted 

cross-hole radar pulse. The model simulated a 

CD radar scan by stepping the transmitter and 

receiver locations in 10-cm intervals along the 

NUMERICAL AND PHYSICAL MODELING OF VERTICAL, PERMEABLE, ZERO-VALENT, REACTIVE-IRON WALLS 5

-1.00

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

1.20

-10 -8 -6 -4 -2 0

TIME, IN NANOSECONDS

NORMALIZED AMPLITUDE

Field data

Ricker wavelet

2 4 6 8 10

Figure 5. Waveform characteristics of the 250-megahertz Ricker wavelet used for the numerical modeling and a 

250-megahertz transmitted radar wave from the fi eld data. 
MODEL

WALL

SUPER-ABSORBING

BOUNDARY

Transmitters Receivers

SATURATED SAND

Relative dielectric permittivity= 25

Electrical conductivity = 

0.01 siemens/meter

12.8 meters (256 cells)

12.8 meters

(256 cells)

2.5 meters

(50 cells)

Figure 6. The two-dimensional fi nite-difference timedomain numerical model geometry used to determine the 

effects of wall edges on radar transmission characteristics.

HOLE IN 

WALL

MODEL

WALL

SUPER-ABSORBING

BOUNDARY

Transmitter Receiver

SATURATED SAND

Relative dielectric permittivity= 25

Electrical conductivity = 

0.01 siemens/meter

12.8 meters 

(256 cells)

12.8 meters

(256 cells)

2.5 meters

(50 cells)

Figure 7. The two-dimensional fi nite-difference timedomain numerical model geometry used to determine the 

effects of wall discontinuities (holes) on radar transmission 

characteristics.

6 Cross-Hole Radar Scanning of Two Vertical, Permeable, Reactive-Iron Walls at the Massachusetts Military Reservation, Cape

Cod, Massachusetts

model boundary parallel to the simulated wall. The 

horizontal separation between the radar transmitter 

and receiver ranged from 5.00 to 7.25 m to simulate 

the distances between boreholes at the fi eld site. 

 To determine the effect of discontinuities on 

cross-hole radar measurements, the vertical wall was 

extended across the entire model except for an opening centered at the midpoint of the wall (fi g. 7). The 

separation of the transmitting and receiving antennas 

was fi xed at 6.30 m, centered about the hole. The 

size of the hole ranged from 0 to 40 cm, in 5-cm 

increments. Relative to the transmitted radar pulse, 

the dimensions of the hole ranged from 0 to almost 

1.7 times the wavelength of the transmitted pulse.

 For each model, the 2D FDTD code produced 

a number of radar waveforms equal to the number 

of transmitter-receiver locations in the model. To 

determine the effect of wall edges and discontinuities 

on the cross-hole radar measurements, the amplitudes 

of the horizontal scans were measured and plotted 

relative to the appropriate independent variable, such 

as depth or hole-size.

 Radar-pulse amplitudes from the edge models 

are shown in fi gure 8. The modeled pulse amplitudes 

were normalized to 1.0 based on an average background pulse amplitude obtained from a model 

without a wall. For the range of horizontal transmitter-receiver separations in this study, the simulated 

radar-pulse amplitude decreased to 0.43 of the normalized background wave amplitude when the modeled CD scan was at the edge of the wall. 

 Radar-pulse waveforms from the hole models 

are shown in fi gure 9. Qualitatively, the amplitude of 

the transmitted radar pulse increases as the aperture of 

the hole increases, approaching the amplitude of the 

background pulse as the size of the hole approaches 

the wavelength of the dominant frequency of the radar 

pulse. The maximum normalized amplitude of the 

transmitted pulse is plotted against the aperture of 

the hole (fi g. 10). Differences in pulse amplitude are 

minor for holes smaller than 0.40 wavelengths (about 

10 cm for a 250-MHz transmitted pulse). These 

results indicate that holes smaller than about 40 percent of the radar-pulse wavelength are not likely to 

be detected.
Figure 8. Two-dimensional fi nite-difference time-domain numerical model radar-pulse amplitude results normalized to 

background amplitudes. [For transmitter (tx) - receiver (rx) separations ranging from 5.50 to 7.00 meters and plotted from 

3.0 meters above top edge to 3.0 meters below top edge of the wall.]

NUMERICAL AND PHYSICAL MODELING OF VERTICAL, PERMEABLE, ZERO-VALENT, REACTIVE-IRON WALLS 7

-35,000

-30,000

-25,000

-20,000

-15,000

-10,000

-5,000

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

95 100 105 110 115 120

TIME, IN NANOSECONDS

MODEL WAVEFORM AMPLITUDE,

 IN MICROVOLTS

No hole

0.208 wavelength (5 centimeter) hole

0.417 wavelength (10 centimete) hole

0.625 wavelength (15 centimeter) hole

0.833 wavelength (20 centimeter) hole

1.042 wavelength (25 centimeter) hole

1.250 wavelength (30 centimeter) hole

1.458 wavelength (35 centimeter) hole

1.666 wavelength (40 centimeter) hole

Figure 9. Two-dimensional fi nite-difference time-domain numerical model radar-waveform results plotted as a function of 

time. [Transmitter-receiver separation is 6.30 meters. Antennas are centered about holes ranging in aperture from 0 to 

1.666 wavelengths (0 to 40 cm). ]
Figure 10. Two-dimensional fi nite-difference time-domain numerical model results showing normalized maximum 

peak-to-peak amplitude plotted against hole aperture.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

HOLE APERTURE, IN WAVELENGTHS

NORMALIZED PEAK-TO-PEAK AMPLITUDE

0 5 10 15 20 25 30 35 40

HOLE APERTURE, IN CENTIMETERS

8 Cross-Hole Radar Scanning of Two Vertical, Permeable, Reactive-Iron Walls at the Massachusetts Military Reservation, Cape

Cod, Massachusetts

Physical Modeling

Although the numerical modeling results 

indicate that wall edges and discontinuities will have 

predictable and measurable changes in the amplitude 

of a transmitted radar pulse during cross-hole radar 

measurements, it is appropriate to question the validity of the results. For example, are the pulseamplitude characteristics predicted by the numerical 

models consistent with real data? Can the numericalmodeling results be used reliably as a template to 

interpret fi eld data? Because the fi eld problem is 

innovative and the borehole-radar method is relatively 

new, data from similar problems were not found. 

Therefore, the numerical-modeling results were compared to radar data obtained from laboratory-scale 

physical models that attempted to simulate the geometry and dimensions of the numerical models relative 

to the wavelength of the transmitted pulse. Scaled 

physical modeling was conducted at the Aldridge 

Geophysical Imaging Laboratory at Columbia University.

 The laboratory-scale physical model was 

constructed from an ordinary aquarium with interior 

dimensions of 119.4 by 43.3 by 75.0 cm. The 

aquarium was fi lled with sand saturated with water. 

A perfect conductor was simulated by wrapping 20 

layers of aluminum foil around a cardboard template 

(fi g. 11). Two Malå GeoScience RAMAC antennas 

with approximate center frequencies of 900 MHz 

were used as the transmitter and receiver (fi g. 12). 

Radar-transmission data were acquired by moving the 

transmitting and receiving antennas, positioned on 

opposite sides of the tank 43.3 cm apart, along the 

119.4-cm-long horizontal axis of the tank in 1-cm 

increments. Radar traces were recorded at 55,828 

MHz using 1,024 samples per trace. This sampling 

rate was selected to ensure that frequency components 

within the radar-pulse frequency band were properly 

recorded. 

 Another model was constructed with the 

aluminum foil template extending across one-half of 

the tank (fi g. 13). This model was designed as a 

physical analog to the fi eld-scale problem simulated 

by the wall-edge numerical models. Two additional 

models were constructed with the aluminum foil 

template extending across the entire tank. In these 

models, a hole was cut into the center of each sheet 
Figure 11. Physical model assembly with the perfectconductor analog extending half of the length of the tank.

Figure 12. Conceptual diagram of the physical model

assembly consisting of a tank filled with saturated sand and

a perfect-conductor analog extending the length of the tank.

900 megahertz

radar antenna

Perfect-conductor analog

extending half the

length of the tank

Tank filled

with

saturated

sand

119.4 centimeters

43.4 centimeters

75.0 centimeters

900 megahertz

radar antenna

Figure 13. Conceptual diagram of the physical model

assembly with a perfect-conductor analog extending half of

the length of the tank.

NUMERICAL AND PHYSICAL MODELING OF VERTICAL, PERMEABLE, ZERO-VALENT, REACTIVE-IRON WALLS 9

900 megahertz

radar antenna

Perfect-conductor analog

extends full length of the tank

119.4 centimeters

43.4 centimeters

75.0 centimeters

900 megahertz

radar antenna

Tank filled

with

saturated

sand

(fig. 14). The sizes of the holes were 2 cm and 11 cm,

corresponding to about 0.36 and 2.00 wavelengths,

respectively. These models were designed as physical

analogs to the field-scale problem simulated by the

hole-in-wall numerical models.

To determine background transmitted-pulse

amplitudes and wavelengths, measurements were

made across the tank containing only saturated sand.

Measurements also were made with a continuous aluminum foil template placed in the tank to verify the

assumption that the aluminum foil would simulate a

Figure 14. Conceptual diagram of the physical model

assembly containing a perfect-conductor analog with holes

with apertures of 0.36 and 2.00 wavelengths (2 and 11

centimeters).

900 megahertz

radar antenna

Perfect-conductor analog

extending full length of the tank

Tank filled

with

saturated

sand

900 megahertz

radar antenna

Holes in

wall

119.4 centimeters

43.4 centimeters

75.0 centimeters
numerical-model results for the case of a borehole 

separation of 5 m. The transmitted pulse amplitude 

is observed to decrease as the antenna positions 

approach the edge of the aluminum model wall. The 

transmitted pulse amplitude is expected to decrease in 

areas where the wall is present and increase with 

distance away from the wall. The edge of the aluminum sheets correlates with the position of the scan 

where the normalized transmitted pulse amplitude 

decreases to about 0.41 (fi g. 16). The characteristics 

of transmitted pulse amplitude with respect to conductor edges observed in the physical model correlates closely with the results of the 2D FDTD model, 

where the position of the wall edge corresponds to a 

decrease in normalized radar-pulse amplitude of about 

0.43. 

 Cross-tank radar-wave amplitudes from the 

models constructed with a hole cut in a continuous 

aluminum foil template are shown in fi gure 17. 

Radar-wave amplitudes, normalized to the average 

background pulse amplitude, are plotted against 

antenna position. The transmitted pulse amplitude 

is observed to increase as the antenna position 

approaches the position of the hole in the aluminum 

sheets. The changes in transmitted pulse amplitude 

and the relative magnitude of the amplitude changes 

with respect to the size and location of the holes 

observed in the physical model data correlate closely 

Figure 15. A waveform transmitted through the background physical model (no wall) and a waveform transmitted through 

the perfect-conductor analog. [The maximum amplitude of the waveform transmitted through the perfect-conductor analog is 

about 0.1 percent of the maximum amplitude of the waveform transmitted through the background physical model.]

perfect conductor and prevent the penetration of the 

radar pulse across the tank. A background radar trace 

is shown in fi gure 15. The average wavelength of the 

transmitted pulse in the saturated sand of the laboratory tank was 5.5 cm, with an average amplitude of 

about 40,000 mV. A cross-tank radar trace recorded 

after a continuous aluminum foil template was placed 

in the tank is also shown in fi gure 15. The amplitude 

of this pulse is about 0.1 percent of the background 

pulse amplitude, indicating that the aluminum sheet is 

useful for modeling a perfect conductor.

 The wavelength of the pulse in saturated sand 

produced by the 250-MHz borehole antennas used for 

the fi eld study was 24 cm, about 4 times longer than 

the wavelength of the antennas used for the physical 

model. Relative to the transmitted pulse wavelength, 

the laboratory tank dimensions correlate with those 

numerical models that simulate a borehole separation 

of about 2 m. The 2-cm and 11-cm holes in the 

aluminum sheets correlate with numerical models 

that contain 8.7-cm and 48-cm-diameter holes, 

respectively.

 Maximum cross-tank radar pulse amplitudes 

from the half-wall physical model are shown plotted 

against antenna positioning in fi gure 16. Pulse amplitudes from the physical model have been normalized 

to the average background pulse amplitude. The 

physical-model data are shown juxtaposed to the 

10 Cross-Hole Radar Scanning of Two Vertical, Permeable, Reactive-Iron Walls at the Massachusetts Military Reservation, 

Cape Cod, Massachusetts
COLLECTION, PROCESSING, AND 

ANALYSIS OF GEOPHYSICAL DATA

 In this study, conventional geophysical 

logging and cross-hole radar scanning were 

conducted at the fi eld site before and after 

iron injection. The conventional logs included 

electromagnetic (EM)-induction and borehole 

deviation. The conventional geophysical logging 

was conducted to (1) identify lithologic or waterquality changes that could affect the planning or 

implementation of the iron injection, (2) determine 

the geometry of the boreholes, and (3) provide a 

record of conditions near the observation boreholes 

to determine if any effects of the hydraulic-fracturing 

process could be measured using EM induction 

logging. 

 A total of 26 observation boreholes were 

installed at the fi eld site. Of these, 20 were 

used for the study (fi g. 18). Most boreholes were 

7.62-cm diameter PVC cased boreholes drilled to 

depth of about 46 m. Five boreholes (RW-04, RW-05, 

RW-11, RW-13, and RW-21) were “Slope-Indicator”

boreholes that utilize a specialized 6.78-cm PVC 

casing. The Slope-Indicator wells were used by the 

University of Waterloo to determine deviation from 

vertical.

 Five boreholes (RW-03, RW-04, RW-05, 

RW-11, and RW-12) were damaged during the wall 

installation and could not be used for additional radar 

logging. Three new boreholes (RW-03A, RW-04A, 

and RW-11A) were installed to replace the damaged 

boreholes. Borehole RW-21 deviated through the 

expected path of the wall, thus it could not be used to 

interpret accurately the wall location using cross-hole 

methods.

Electromagnetic Induction

EM-induction logs record the electrical conductivity or resistivity of materials or combinations 

of materials, such as the sediments and ground water, 

surrounding the borehole. EM-induction logging was 

conducted in every available borehole in the study 

area. The electrical conductivity of the formation was 

measured at 3.0-cm increments with a Mount Sopris 

2PIA Poly Induction Probe. The probe has a vertical 

resolution of 40 cm and a radius of penetration of 100 

cm (McNeill and others, 1990). EM-induction logs 

collected after iron injection were examined to deter-

-5

-4

-3

-2

-1

0

1

2

3

4

5

ANTENNA CENTER POSITION, IN WAVELENGTHS FROM EDGE OF WALL

0.0 0.2 0.4 0.6 0.8 1.0 1.2

NORMALIZED RADAR PEAK-TO-PEAK AMPLITUDE

Numerical model

Physical model MODEL WALL

Figure 16. Radar data from the half-wall physical model 

overlain with results from the half-wall numerical model [for 

an antenna separation of 5.00 meters].

Figure 17. Normalized peak-to-peak amplitudes for waves 

transmitted in the physical model through the perfectconductor analog for holes of 0.36 and 2.00 wavelengths 

(2 and 11 centimeters).

COLLECTION, PROCESSING, AND ANALYSIS OF GEOPHYSICAL DATA 11

with the results of the 2D FDTD model.

 The correlation between the amplitude trends 

predicted by the 2D FDTD numerical model and the 

amplitude trends observed in radar data acquired from 

the physical wall-edge and hole-in-wall models indicates that the numerical models can be used to interpret amplitude trends observed in cross-hole radar 

fi eld data.
mine if the hydraulic-fracturing method resulted in

the deposition of iron near the observation boreholes.

Processing of the EM-induction data included

filtering and generating vertical sections using data

from boreholes along the same row. The EM-induction logs were filtered with a 21-point moving-average filter to reduce random noise and the effects

of small-scale spatial heterogeneities. EM-induction

data from boreholes in the same row were combined

into cross-section plots. EM-induction data collected

in the northern row of boreholes (RW-01 to RW-07)

after completion of the hydraulic fracturing are shown

in figure 19. In this figure, an area with very high

conductivity is present in boreholes RW-03, RW-03A,

and RW-04A at a depth of about 28 m (fig. 18). These

data indicate that highly conductive materials, interpreted as iron, were emplaced near these boreholes as

a result of the injection process; and demonstrate, at

least in this specific area, that the injection process

resulted in a three-, rather than two-, dimensional

distribution of iron.

RW-11

RW-01

RW-06

RW-02

RW-07

RW-17

RW-22

RW-23

RW-08

RW-09

RW-18 RW-19

RW-20

RW-16

RW-15

RW-10

RW-13

RW-14

RW-05

RW-03

A-WALL

B-WALL

0 5 10 METERS

N

W E

RW-12

RW-04

X

X

X

X X

RW-11A

RW-04A

RW-03A

X

Borehole and

identifier

Damaged borehole

and identifier

Supplemental borehole

and identifier

Transmission raypath

EXPLANATION

RW-05

RW-01

RW-04A

0 10 20 30 FEET

Figure 18. Map view of the study area showing observation boreholes and transmission raypaths, Massachusetts Military

Reservation, Cape Cod, Mass. [Damaged boreholes were deformed during the iron-wall installation and were unusable

for further radar data collection. The supplemental boreholes were drilled after the iron injection to replace the damaged

boreholes.]

-800 200 -800 200 -800 200 -800 200 -800 200 -800 200 -800 200

CONDUCTIVITY, IN MILLISIEMENS PER METER

25

30

35

40

45

20 RW-01 RW-02 RW-03 RW-03A RW-04A RW-06 RW-07

DEPTH, IN METERS BELOW TOP OF CASING Figure 19. Borehole electromagnetic logging of boreholes

north of the A-wall after the A-wall installation,

Massachusetts Military Reservation, Cape Cod, Mass.

[Negative values indicate the presence of highly conductive

materials near the boreholes.]

12 Cross-Hole Radar Scanning of Two Vertical, Permeable, Reactive-Iron Walls at the Massachusetts Military Reservation,

Cape Cod, Massachusetts
Borehole Deviation

Borehole deviation logs record the threedimensional (3D) geometry of a borehole. Borehole

deviation logging was conducted to determine accurately the vertical orientation of the observation

boreholes used for this study. This information

is required to analyze the cross-hole radar data properly. Two independent borehole deviation surveys

were conducted using a Century 9620 deviation and

gamma probe and an Icefield Instruments, Inc. MI-03

series deviation tool. The Century tool was used to

measure the deviation of boreholes RW-01 through

RW-23 before the wall installation. The Icefield tool,

which is dip based and unaffected by the presence of

iron, was used after the iron injection to determine

the geometry of boreholes RW-03A, RW-04A, and

RW-11A.

Borehole deviation logs were combined with

field-site survey information to produce 3D representations of the boreholes. These data were used to

correctly position the locations of cross-hole radar

traces. The borehole deviation data indicate that several boreholes deviate significantly from vertical.

Cross-Hole Radar Scanning

Cross-hole radar field data were acquired

with a Malå GeoScience RAMAC borehole-radar

system using electric-dipole antennas with center frequencies in air of about 100 and 250 MHz. Radar

scans were conducted in 20 observation boreholes in

three rows parallel to the injection zones (fig. 18). A

radar scan of the region between two boreholes was

constructed from cross-hole measurements acquired

by moving a radar transmitter and receiver in unison

at 10-cm increments from the top of the casing to the

bottom of the borehole. At each antenna position,

32 traces were stacked (added) and recorded using a

sampling frequency of 2,635 MHz and 1,024 samples

per trace. The sampling rate was selected to ensure

that frequency components within the radar-pulse frequency band were properly recorded.

Processing the cross-hole radar data was limited to band-pass filtering to reduce random noise.

After filtering, the maximum peak-to-peak amplitude

of the direct wave from each trace was measured

(fig. 15). Under the assumption that iron was not

introduced into sediments below a depth of 40 m, the

amplitudes measured for each borehole-pair were normalized relative to the average amplitude of “background” cross-hole measurements below 40-m depth.

Thus, a normalized value near 1.00 indicates the pulse

amplitude is consistent with a background value.

After normalization, amplitude data from

each pair of rows were combined into cross sections

and contoured. A contoured background cross-section image from the borehole pairs straddling the

B-wall is shown in figure 20. Contoured post-injection cross-section images from borehole pairs straddling the A- and B-wall zones are shown in figures

21 and 22. In the post-injection plots of the Aand B-wall zones, strong amplitude decreases are

observed in several areas of the cross-section coincident with the depths of iron injection (24 to 37 m).

COLLECTION, PROCESSING, AND ANALYSIS OF GEOPHYSICAL DATA 13

Figure 20. Pre-injection direct-wave amplitudes across

the B-wall, Massachusetts Military Reservation, Cape Cod,

Mass.

Before iron injection, it was assumed that

the distribution of iron between borehole pairs would

be identified by analyzing the differences in the normalized amplitudes between pre- and post-injection

scans; however, because the hydraulic-fracturing process damaged five observation boreholes, the loss of

these boreholes resulted in large data gaps (fig. 23)

that prevented the use of a differencing approach.

Therefore, normalized amplitudes from post-injection

field-data were compared directly to the results of the

numerical modeling.

Based on the numerical- and physical-modeling results, the following method was used to analyze
Figure 21. Post-injection direct-wave amplitudes across

the A-wall, Massachusetts Military Reservation, Cape Cod,

Mass.

Figure 22. Post-injection direct-wave amplitudes across

the B-wall, Massachusetts Military Reservation, Cape Cod,

Mass.

Figure 23. Map view of the study area showing observation boreholes and transmission raypaths lost due to damaged

boreholes, Massachusetts Military Reservation, Cape Cod, Mass. [Damaged boreholes were deformed during the iron wall

installation, and were unusable for radar data collection. The transmission raypaths from well pairs involving the damaged

boreholes are shown with dashed lines. The supplemental boreholes were drilled after the iron injection to replace the

damaged boreholes.]

14 Cross-Hole Radar Scanning of Two Vertical, Permeable, Reactive-Iron Walls at the Massachusetts Military Reservation,

Cape Cod, Massachusetts

RW-11

RW-01

RW-06

RW-02

RW-07

RW-17

RW-22

RW-23

RW-08

RW-09

RW-18 RW-19

RW-20

RW-16

RW-15

RW-10

RW-13

RW-14

RW-05

RW-03

RW-21

A-WALL

B-WALL

N

W E

RW-12

RW-04

X

X

X R

X W-11A

RW-04A

RW-03A

Transmission raypath

eliminated by loss of

damaged boreholes

0 5 10 METERS

0 10 20 30 FEET

X

Borehole and

identifier

Damaged borehole

and identifier

Supplemental borehole

and identifier

Transmission raypath

EXPLANATION

RW-05

RW-01

RW-04A

X
one extends about 10.0 m horizontally and 6.0 m

vertically from about 25.0 to 31.0 m below land

surface, and another zone extends about 8.0 m

horizontally and 3.0 m vertically from about 31.5 to

34.5 m below land surface. For the B-wall (fig. 26),

the contouring outlines a large irregularly shaped lowamplitude area that extends about 9.0 m horizontally

and 7.5 m vertically from about 27 to 34.5 m below

Figure 24. Normalized model-wall amplitudes for a

3.10-meter wall and the normalized field-data amplitudes

from the common-depth radar survey between boreholes

RW-20 and RW-13, Massachusetts Military Reservation,

Cape Cod, Mass.

-1.7

4.3

M

ODEL TRANSMITTER-RECEIVER POSITION,

IN METERS BELO

W TOP EDGE OF W

ALL

30

31

32

33

34

35

36

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

NORMALIZED PEAK-TO-PEAK AMPLITUDE

DEPTH OF FIELD DATA, IN METERS BELO

W TOP OF CASING

Numerical model data

Field data

M

ODEL W

ALL 3.10 METERS

4.0

-1.0

0.0

1.0

0.5

-0.5

-1.5

1.5

2.0

2.5

3.0

3.5

COLLECTION, PROCESSING, AND ANALYSIS OF GEOPHYSICAL DATA 15

the field data: (1) the depth where normalized postinjection amplitudes decreased to 0.43 was interpreted

as a wall edge (fig. 8); (2) areas bounded by wall

edges where amplitudes were below 0.43 were interpreted as wall zone; and (3) areas in a wall zone

where normalized amplitudes exceeded 0.43 were

interpreted as holes in a section of wall.

An example of this analysis applied to crosshole radar data from the scan between boreholes

RW-20 and RW-13 (fig. 18) is shown in figure 24.

The field data are shown juxtaposed to the results of

the numerical modeling. The vertical section of wall

interpreted between boreholes RW-20 and RW-13 is

about 3.10 m in height, extending from 31.7 m to 34.8

m below land surface. No holes are interpreted in this

section of B-wall.

This analysis method was applied to the postinjection amplitude data from the A and B walls.

Normalized cross-hole amplitude data below the 0.43

contour are shown for the A- and B-walls in figures

25 and 26. For the A-wall (fig. 25), the contouring

outlines two irregularly shaped low-amplitude areas;

Figure 25. Post-injection direct-wave amplitudes across

the A-wall showing normalized amplitudes of less than 0.43,

Massachusetts Military Reservation, Cape Cod, Mass.

Figure 26. Post-injection direct-wave amplitudes across

the B-wall showing normalized amplitudes of less than 0.43,

Massachusetts Military Reservation, Cape Cod, Mass.
land surface. The continuous low-amplitude areas are 

interpreted as zones of iron wall.

 Based on the numerical and physical modeling results, no observations in either the A- or B-walls 

indicated the presence of holes in the wall zones. 

This indicates that (1) iron in the wall zones is distributed in a generally continuous manner; (2) holes, if 

any, exist at scales smaller than the resolution limit of 

the radar antennas and acquisition geometry used for 

this study (about 10 cm); or (3) irregularities in iron 

distribution are such that holes in one area are masked 

by accumulations of iron in other areas.

SUMMARY

 A pilot-scale study was conducted by the U.S. 

Army National Guard (USANG) at the Massachusetts 

Military Reservation (MMR) on Cape Cod, Massachusetts, to assess the use of a hydraulic-fracturing 

method to create vertical, permeable walls of zerovalent iron to passively remediate ground water 

contaminated by chlorinated solvents where the contamination is present at depths that exceed the practical construction limits of conventional iron walls. 

The study was conducted near the source area of 

the CS-10 plume, a chlorinated-solvents plume that 

underlies the MMR. In the study area, ground water 

is contaminated from about 24 to 37 m below land 

surface. A treatment zone consisting of two parallel, 

reactive-iron walls 12 m long, 0.15 m thick, extending 

from 24 to 37 m below land surface, and separated by 

about 6.1 m, was designed by the USANG to intersect 

and remediate a part of the CS-10 plume. 

 Because electrical conductors, such as iron, 

absorb electromagnetic energy, the U.S. Geological 

Survey used a cross-hole, common-depth, radarscanning method to test the continuity and estimate 

the lateral and vertical extent of the two reactive-iron 

walls. The cross-hole radar surveys were conducted 

in boreholes on opposite sides of the iron injection 

zones using electric-dipole antennas with dominant 

center frequencies (in air) of 100 and 250 MHz. 

The amplitudes of radar waves crossing the injection 

zones decreased signifi cantly between the pre- and 

post-injection surveys. Electromagnetic-induction 

data also showed signifi cant changes between preand post-injection surveys of boreholes near the 

injection zones.

 Results from two-dimensional fi nite-difference time-domain numerical modeling and from laboratory-scale physical modeling were used to interpret 

the changes in radar amplitude observed in the fi eld 

data. The numerical and physical models simulate 

a wall of perfectly conducting material embedded in 

saturated sand. Results from both the numerical and 

physical models indicate that the amplitude of a radar 

pulse transmitted across the edge of a conductive wall 

is about 43 percent of the amplitude of a radar pulse 

transmitted through background material. Simulation 

of radar pulse transmission through holes in perfectly 

conducting media indicates that holes with diameters 

less than about 40 percent of the wavelength of the 

dominant frequency of the radar pulse are not likely to 

be detected and that the amplitude of the transmitted 

radar pulse will increase as the diameter of the hole 

increases, approaching background levels as the hole 

aperture approaches the wavelength of the dominant 

frequency in the radar pulse.

 Based on the results of the numerical and 

physical modeling, interpretation of the radar fi eld 

data indicates that neither the A-wall nor the B-wall 

contain holes larger than about 10 cm, the resolution 

limit of the radar scanning in this study. However, the 

iron in the northern A-wall appears to be distributed 

in two discrete zones: an upper zone about 10-m 

wide, extending from about 25.0 to 31.0 m below land 

surface and a lower zone about 8-m wide, extending 

from about 31.5 to 34.5 m below land surface. The 

iron in the southern B-wall appears to be distributed 

continuously in a zone about 9-m wide extending 

from about 27.0 to 34.5 m below land surface. 

 The interpretation of the fi eld data suggests 

that (1) the hydraulic-fracturing method introduced 

iron into the subsurface, but not in the dimensions 

originally proposed; (2) the iron within the treatment 

zones is distributed in a generally continuous manner; 

and (3) excluding the discontinuity in the A-wall, 

holes within the iron treatment zone, if any, exist at 

scales smaller than the resolution limit of the radar 

antennas and acquisition geometry used for this study. 

The cross-hole radar method appears to have been 

an effective method for delineating the distribution of 

iron in the two walls; however, the veracity of the 

results cannot be ascertained without excavation or 

drilling into the treatment zone.

16 Cross-Hole Radar Scanning of Two Vertical, Permeable, Reactive-Iron Walls at the Massachusetts Military Reservation, 

Cape Cod, Massachusetts
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 various pagination.

Carmichael, R.S., 1989, Practical handbook of

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REFERENCES CITED 17




Lane and others, 2001--Cross-Hole Radar Scanning of Two Vertical, Permeable, Reactive-Iron Walls at the Massachusetts Military 

Reservation, Cape Cod, Massachusetts

U.S. Geological Survey Water Resources Investigations Report 00-4145