U.S. Department of the Interior

U.S. Geological Survey

Toxic Substances Hydrology Program

Diffusion and Drive-Point Sampling to 

Detect Ordnance-Related Compounds in

Shallow Ground Water Beneath Snake Pond,

Cape Cod, Massachusetts, 2001–02

By DENIS R. LEBLANC

Water-Resources Investigations Report 03-4133

Prepared in cooperation with the

ARMY NATIONAL GUARD BUREAU

Northborough, Massachusetts

2003
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of trade, product, or firm names in this report is for identification purposes only and does 

not imply endorsement by the U.S. Government.

For additional information write to:

Chief, Massachusetts-Rhode Island District

U.S. Geological Survey

10 Bearfoot Road

Northborough, MA 01532

or visit our Web site at

http://ma.water.usgs.gov

Copies of this report can be purchased from:

U.S. Geological Survey

Branch of Information Services

Box 25286

Denver, CO 80225-0286
 III

CONTENTS

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

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

Acknowledgments.............................................................................................................................................................. 2

Field Investigation and Results.......................................................................................................................................... 4

Diffusion-Sampler Design ....................................................................................................................................... 4

Laboratory Test of Diffusion Samplers................................................................................................................... 5

Diffusion Sampling of Ground Water..................................................................................................................... 6

August–September 2001 Transect................................................................................................................. 6

September–October 2001 Transects.............................................................................................................. 12

Drive-Point Sampling of Ground Water ................................................................................................................. 15

Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond........................................................... 18

Summary............................................................................................................................................................................. 19

References Cited................................................................................................................................................................. 19

FIGURES

1. Map showing locations of Camp Edwards military ranges, Snake Pond, test borings with 

validated detections of explosives and perchlorate, and altitude of the water table, 

Cape Cod, Massachusetts, 2001–02.............................................................................................................. 3

2. Photograph of diffusion sampler showing inner core, slip-on end caps, cellulose membrane, 

and outer mesh................................................................................................................................................ 5

3–5. Maps showing:

3. Locations of diffusion samplers set in the bottom sediments of Snake Pond, August–October 2001 7

4. Locations of validated detections of ordnance-related compounds in diffusion and drivepoint water samples collected from bottom sediments of Snake Pond, August 2001– 

March 2002............................................................................................................................................. 14

5. Locations of temporary drive points installed in the bottom sediments of Snake Pond, 

December 2001 and March 2002.......................................................................................................... 16

TABLES

1. Results of laboratory tests of prototype diffusion samplers constructed of tubular cellulose 

membranes, July 2001.................................................................................................................................... 6

2. Locations, site identifiers, and installation and retrieval dates of diffusion samplers set in the

bottom sediments of Snake Pond, Cape Cod, Massachusetts, August–October 2001............................... 8

3. Target chemical compounds included in analysis of diffusion and drive-point ground-water 

samples collected beneath Snake Pond ......................................................................................................... 12

4. Validated detections of ordnance-related compounds in diffusion and drive-point samples 

collected from the pond-bottom sediments of Snake Pond, August 2001–March 2002............................ 13

5. Locations, site identifiers, sampling depths and dates, and specific conductance of water samples 

collected from a temporary well point driven into the bottom sediments of Snake Pond, December 

2001 and March 2002..................................................................................................................................... 17
IV 

CONVERSION FACTORS, VERTICAL DATUM, WATER-QUALITY 

INFORMATION, AND ABBREVIATIONS

CONVERSION FACTORS

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 x °C) + 32

VERTICAL DATUM

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 

1929)—a geodetic datum derived from a general adjustment of the first-order level nets of the United States 

and Canada, formerly called the Sea Level Datum of 1929.

Altitude, as used in this report, refers to distance above or below sea level.

WATER-QUALITY INFORMATION

Chemical concentration is given in units of milligrams per liter (mg/L) or micrograms per liter (μg/L). 

Milligrams and micrograms per liter are units expressing the mass of the solute per unit volume (liter) of 

water. One thousand micrograms per liter is equivalent to 1 milligram per liter. Micrograms per liter is 

approximately equivalent to “parts per billion” and milligrams per liter is approximately equivalent to 

“parts per million” in dilute water.

Multiply By To obtain

foot (ft) 0.3048 meter (m)

inch (in.) 2.54 centimeter (cm)

millimeter (mm) 0.03937 inch (in.)

mile (mi) 1.609 kilometer (km)

liter (L) 0.2642 gallon (gal)

ABBREVIATIONS

ARNG Army National Guard

GPS Global positioning system

HMX Octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine

mL milliliter

mm millimeter

MMR Massachusetts Military

Reservation

MWCO Molecular-weight cutoff

PDA Photo diode array

PETN Pentaerythritol tetranitrate

PVC Polyvinyl chloride

RDX Hexahydro-1,3,5-trinitro-1,3,5-

triazine

STL Severn Trent Laboratory

USGS U.S. Geological Survey

USEPA U.S. Environmental Protection

Agency

VOC Volatile organic compound

μg/L microgram per liter

μm micrometer

μS/cm microsiemens per centimeter at

25 degrees Celsius
Abstract 1

Diffusion and Drive-Point Sampling to 

Detect Ordnance-Related Compounds in 

Shallow Ground Water Beneath Snake Pond, 

Cape Cod, Massachusetts, 2001–02

By Denis R. LeBlanc

ABSTRACT

Diffusion samplers and temporary drive points 

were used to test for ordnance-related compounds in 

ground water discharging to Snake Pond near Camp 

Edwards at the Massachusetts Military Reservation, 

Cape Cod, MA. The contamination resulted from 

artillery use and weapons testing at various ranges 

upgradient of the pond.

The diffusion samplers were constructed with 

a high-grade cellulose membrane that allowed 

diffusion of explosive compounds, such as RDX 

(Hexahydro-1,3,5-trinitro-1,3,5-triazine) and HMX 

(Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), 

into deionized water inside the samplers. Laboratory 

tests confirmed that the cellulose membrane was 

permeable to RDX and HMX. One transect of 22 

diffusion samplers was installed and retrieved in 

August–September 2001, and 12 transects with a 

total of 108 samplers were installed and retrieved in 

September–October 2001. The diffusion samplers 

were buried about 0.5 feet into the pond-bottom 

sediments by scuba divers and allowed to equilibrate 

with the ground water beneath the pond bottom for 

13 to 27 days before retrieval. Water samples were 

collected from temporary well points driven about 2–

4 feet into the pond bottom at 21 sites in December 

2001 and March 2002 for analysis of explosives and 

perchlorate to confirm the diffusion-sampling results.

The water samples from the diffusion samplers 

exhibited numerous chromatographic peaks, but 

evaluation of the photo-diode-array spectra indicated 

that most of the peaks did not represent the target 

compounds. The peaks probably are associated with 

natural organic compounds present in the soft, 

organically enriched pond-bottom sediments. The 

presence of four explosive compounds at five widely 

spaced sites was confirmed by the photo-diode-array 

analysis, but the compounds are not generally found 

in contaminated ground water near the ranges. No 

explosives were detected in water samples obtained 

from the drive points. Perchlorate was detected at 

less than 1 microgram per liter in two drive-point 

samples collected at the same site on two dates about 

3 months apart. The source of the perchlorate in the 

samples could not be related directly to other 

contamination from Camp Edwards with the 

available information.

The results from the diffusion and drive-point 

sampling do not indicate an area of ground-water 

discharge with concentrations of the ordnancerelated compounds that are sufficiently elevated to be 

detected by these sampling methods. The diffusion 

and drive-point sampling data cannot be interpreted 

further without additional information concerning the 

pattern of ground-water flow at Snake Pond and the 

distributions of RDX, HMX, and perchlorate in 

ground water in the aquifer near the pond.
2 Diffusion and Drive-Point Sampling to Detect Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond, Cape Cod, MA, 2001–02

INTRODUCTION

Military activities at Camp Edwards at the 

Massachusetts Military Reservation (MMR) on western 

Cape Cod (fig. 1) since the early 1900s have resulted in 

contamination of the ground water by ordnance-related 

compounds such as RDX, HMX, and perchlorate (Army 

National Guard Bureau, 2002). The U.S. Army National 

Guard (ARNG) is conducting studies to locate and 

describe the contaminants, and to develop methods to 

remediate contaminated soils and ground water at the 

military reservation (Army National Guard Bureau, 

2003). The studies have shown that the contaminants are 

present in various plumes that extend from the reservation 

toward ground-water discharge areas at ponds and the 

coast.

In November 2000, RDX was detected in 

monitoring wells near Snake Pond, which is an 83-acre 

glacial kettle-hole pond that is located southeast of the 

Camp Edwards training area (fig. 1) and has a maximum 

depth of about 33 ft (Massachusetts Division of Fisheries 

and Wildlife, 1993). The suspected source of the 

contamination is various artillery ranges, also known as 

the J-ranges, on the southeastern section of the reservation 

(AMEC, 2002a).

Ground water in this area flows southeastward from 

the top of the water-table mound that underlies western 

Cape Cod toward Snake Pond, which is a ground-water 

flow-through pond (Winter and others, 1998) that has no 

surface-water inlet or outlet. Snake Pond is in direct 

hydraulic contact with the aquifer, which is composed of 

permeable sand and gravel glacial outwash (Masterson 

and others, 1996). Ground-water-flow modeling of the 

area (Walter and others, 2002; AMEC, 2001, 2002b) 

indicated that the contaminants could discharge into the 

northern half of Snake Pond, including a shallow northern 

cove that is separated from the larger southern area of the 

pond by a low peninsula that is submerged during periods 

of high water levels (fig. 1). Test drilling in May 2001 

indicated that RDX was present in the ground water 

beneath the peninsula (AMEC, 2001).

Various contaminant plumes of volatile organic 

compounds (VOCs) from the MMR that intersect ponds 

near the base discharge to these ponds near their 

shorelines. There were concerns that the ordnance-related 

compounds might similarly discharge near the northern 

shore of Snake Pond. Diffusion samplers buried in pondbottom sediments had been used successfully to detect 

and delineate the discharge areas of the VOC plumes at 

the other ponds (Savoie and others, 2000). Therefore, the 

U.S. Geological Survey (USGS), in cooperation with the 

Army National Guard Bureau, used diffusion samplers to 

test for the presence of the ordnance-related compounds in 

shallow ground water beneath Snake Pond during 2001–

02. The results of this investigation were used to guide 

additional test drilling near Snake Pond (AMEC, 2002b) 

This report describes the construction and testing of the 

diffusion samplers, the application and results of diffusion 

sampling at Snake Pond, and subsequent drive-point 

sampling to confirm the diffusion-sampler results.

ACKNOWLEDGMENTS

Access to Snake Pond was graciously granted by 

Faith Willard of Camp Good News. The diffusion 

samplers were installed and retrieved with the assistance 

of Timothy McCobb, Michael Columbo, Jennifer Savoie, 

Andrew Massey, Joshua Koch, Kathryn Hess, Dann 

Blackwood, Kenneth Parolski, Barry Irwin, and Michael 

Casso of the U.S. Geological Survey. Analysis of the 

water samples was completed with the assistance of James 

Madison of Severn Trent Laboratories and Mark Grant, 

Elizabeth Wessling, Timothy Dwyer, and Herbert Colby 

of AMEC Earth & Environmental, Inc. David Hill and 

Benjamin Gregson of the Camp Edwards Impact Area 

Groundwater Study provided valuable technical and 

financial support. The review comments concerning this 

report of Don Vroblesky, Peter Church, and Gail Moede 

of the U.S. Geological Survey also are appreciated.
Acknowledgments 3

280,800 282,200

827,600

826,100

U.S. Geological Survey digital data Universal Transverse Mercator Projection

Zone 19, 1:24,000 1991, Massachusetts State Plane Coordinate System Datum is NAD 83 in meters.

300 METERS

71o 70o

42o30'

41o

30'

TEST BORING WITH VALIDATED DETECTIONS OF EXPLOSIVE COMPOUNDS OR 

 PERCHLORATE AS OF APRIL 2002 (AMEC, 2002a)

MILITARY RANGE

Massachusetts Military Reservation

Area of

figures 3-5

MASSACHUSETTS

Cape Cod

Atlantic Ocean

Mass. Military 

Reservation

Study Area

Snake Pond 

Weeks 

Pond

0

0 100 200

500 1,000 FEET

65.5

68.0

67.0

67.5

66.5

66.0

66.0

EXPLANATION

WATER-TABLE CONTOUR—Shows model-simulated altitude of water table, in feet 

 above sea level. Contour interval 0.5 feet (Walter and others, 2002)

70O

70 30'30" O31'30"

41O

41'30"

41O

40'45"

0 10 20 MILES

2

0 10 20 KILOMETERS 50,000 250,000

330,000 895,000

815,000

Figure 1. Locations of Camp Edwards military ranges, Snake Pond, test borings with validated detections of explosives and perchlorate, and 

altitude of the water table, Cape Cod, Massachusetts, 2001–02.
4 Diffusion and Drive-Point Sampling to Detect Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond, Cape Cod, MA, 2001–02

FIELD INVESTIGATION AND RESULTS

Diffusion samplers operate on the principle of 

chemical diffusion. A sampling fluid, such as deionized 

water, that is free of the contaminants of concern is placed 

inside a sealed tubular membrane that is permeable to the 

targeted contaminants. When buried in pond-bottom 

sediments in areas of ground-water discharge, the sampler 

is immersed in pore water about to discharge to the pond. 

The sampler is left in place long enough for contaminants 

dissolved in the ground water flowing past the sampler to 

diffuse through the membrane into the enclosed water; 

thus, concentrations inside and outside the sampler 

become equal. The sampler is then retrieved, and the 

water is decanted into a container for shipment to the 

laboratory for analysis.

Vroblesky and others (1996) describe the 

development and application of diffusion samplers to 

identify the discharge of VOC plumes to streams. Savoie 

and others (2000) describe the use of diffusion samplers to 

locate two VOC plumes that are discharging to Johns 

Pond near the MMR. Additional studies in which 

diffusion samplers were used to describe the discharge of 

VOC plumes to surface waters are described by Church 

and others (2002). In these studies, polyethylene was 

used as the membrane in the diffusion samplers because 

VOCs can diffuse through this type of plastic.

Diffusion-Sampler Design

The diffusion samplers in this study were intended 

to test for the presence of RDX and HMX. These large 

organic molecules are not VOCs and would not pass 

through the polyethylene membrane used in the earlier 

investigations. The use of cellulose-based membranes for 

diffusion sampling of higher molecular-weight organic 

compounds is being tested by the USGS (Vroblesky and 

others, 2002). The effectiveness of these membranes for 

sampling RDX and HMX was tested in the Snake Pond 

study. Prototype diffusion samplers were constructed of 

various parts, including a rigid inner core, the diffusion 

membrane, and an outer protective mesh (fig. 2). The 

fluid in the samplers was deionized water.

A 1-ft-long section of 2-in. nominal diameter 

butyrene tubing served as the inner core of the sampler. 

About 100 holes (0.25-in. diameter) were drilled through 

the tubing. Polyethylene slip-on caps were placed over 

the ends of the tubing and were also perforated with three 

0.25-in. holes. The holes in the tubing and caps 

allowed for ready exchange of water inside and outside 

of the tubing.

The rigid inner core of the sampler is necessary to 

prevent the collapse of the tubular cellulose membrane 

during the diffusion process. The membrane is permeable 

to water, and the deionized water inside the sampler 

diffuses through the membrane into the surrounding 

ground water as contaminants diffuse in the opposite 

direction into the sampler. Without the rigidity provided 

by the inner core, the membrane would collapse over time 

until chemical equilibrium was established. A rigid inner 

core is unnecessary in samplers made with polyethylene, 

which is not permeable to water.

The diffusion membrane was a high-grade, 

regenerated-cellulose tubular membrane obtained from 

Membrane Filtration Products, Inc. (Item No. 0810-100, 

Seguin, TX). The lay-flat tubing was shipped in a 20-

percent ethanol preservative solution (the tubing can also 

be purchased in a dry form that requires additional 

processing before use). The membrane has a width of 

100 mm, an expanded diameter of about 64 mm (2.5 in.), 

a thickness of 65 μm, and a nominal molecular-weight 

cutoff (MWCO) of 6,000 to 8,000 Daltons (nominal pore 

size of 18 angstroms).

The tubular membrane was cut into sections 

about 2 ft long, then rinsed thoroughly in tap water, 

followed by deionized water, to remove the storage 

solution. A knot was tied in one end of the membrane, 

deionized water was added to partially fill the membrane 

and expand it to its full diameter, and the inner core was 

slipped inside of the membrane, which was then filled to 

the top with deionized water. A knot was tied in 

the top of the membrane to seal in the deionized water. 

The entire assembly was then slipped into a flexible 

plastic mesh (Flexguard II, 2- to 2.5-in.-diameter, M-Line, 

Inc., Brunswick, OH) to protect the membrane from 

abrasion and tears. A completed sampler contained about 

500 mL of deionized water. The samplers were 

stored in deionized water until their deployment, unlike 

the samplers made with polyethylene, which can be 

stored in air.
Field Investigation and Results 5

Mesh Cellulose membrane

Slip-on cap

Inner core

Figure 2. Diffusion sampler showing inner core, slip-on end caps, cellulose membrane, and outer mesh. Mesh is pulled back to show inner components.

Laboratory Test of Diffusion Samplers

The effectiveness of the cellulose-membrane 

diffusion samplers for sampling RDX and HMX was 

tested in the laboratory prior to their use in the field. 

Three test chambers were constructed from 5.5-ft-long 

sections of 3-in.-diameter PVC pipe with rubber end caps. 

The chambers were filled with ground water collected on 

July 12, 2001, from three wells on Camp Edwards. These 

wells had been sampled previously and had contained the 

target compounds at concentrations that were suitable for 

the laboratory tests.

The test chambers were secured in an upright 

position, rinsed thoroughly, and filled with ground water 

from the wells. A diffusion sampler filled with deionized 

water was suspended inside each chamber, and the 

chambers were stored in a dark walk-in refrigerator at 

about 4°C for about 12 days. The prototype diffusion 

samplers were constructed with 1.25-in.-diameter, 1.5-ftlong cores and 75-mm lay-flat cellulose tubular 

membrane that had been purchased in the dry form. The 

total volume of the test chambers was about 8 L, and the 

volume of the diffusion samplers was about 0.35 L. 

About once a day, the chambers were shaken to ensure 

that the water inside the chambers remained mixed.

At the end of the 12-day test period, the samplers 

were retrieved from the test chambers, and the water 

inside the diffusion samplers was decanted into sample 

bottles and shipped to the laboratory for analysis. 

Samples of the water in the annuluses of the test chambers 

were also sent for analysis. The ground water originally 

used to fill the test chambers was not sent to the laboratory 

for analysis.
6 Diffusion and Drive-Point Sampling to Detect Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond, Cape Cod, MA, 2001–02

There was reasonable agreement between the 

measured concentrations of RDX and HMX in 

the water collected from the diffusion samplers and the 

test chambers (table 1). The concentrations from the 

diffusion samplers were about 75 to 80 percent of the 

corresponding concentrations from the water in the 

chambers at the end of the test period. This difference 

probably was caused by the absence of flow in the sealed 

chambers. 

Diffusion Sampling of Ground Water

August–September 2001 Transect

A single transect of 22 diffusion samplers was 

placed in Snake Pond in August 2001 to test the sampling 

method before a larger sampling effort was undertaken. 

The transect was located along the simulated path of 

ground-water flow that intersected the screened interval of 

the monitoring wells on the peninsula where RDX was 

detected in May 2001 (AMEC, 2001, 2002b). The 

simulations indicated that ground water from this interval 

could discharge to Snake Pond as far as 500 ft south 

of the peninsula, so the transect extended from this point 

northward, across the peninsula, to the northern shore of 

the cove (fig. 3).

The samplers were set in the pond by using the 

method described by Savoie and others (2000). The 

transect line was prepared by using fisherman’s sinking 

pot-warp rope with the samplers attached by short strings 

and clips at 50- to 75-ft intervals along the line (table 2). 

Small stainless-steel weights were attached to the slightly 

buoyant samplers so they would sink to the bottom. A 

boat and compass were used to lay the line on the pond 

bottom. The line end points were located with a globalpositioning system (GPS) unit. Scuba divers swam along 

each line and buried the samplers about 0.5 ft into the 

pond-bottom sediments by hand with a trowel.

To retrieve the samplers, divers swam along the 

lines and pulled the samplers out of the sediments. 

The lines were hauled into a boat, where the diffusion 

samplers were unclipped from the line and rinsed with 

pond water to remove mud clinging to the sampler. The 

water inside the samplers was then poured into 500-mL 

amber glass bottles through a small hole snipped in the 

cellulose membrane. The bottles were chilled onsite and 

later shipped to the Severn Trent Laboratory (STL) in 

Burlington, VT, for analysis.

Three quality-control water samples also were sent 

for analysis. The sample identified as the RDX control in 

table 2 was obtained from a diffusion sampler that was 

kept in a 20-L container of water from well MW34M1, 

known to contain RDX, for 7 days. The sample identified 

as the distilled-water control in table 2 was obtained from 

a diffusion sampler that was kept for 14 days in a 20-L 

container of deionized water. The sample identified as the 

water blank in table 2 was obtained directly from the 

deionized water supply used to fill the diffusion samplers.

The diffusion samplers were buried in the pondbottom sediments on August 24, 2001, and retrieved on 

September 7, 2001. This 13-day period was considered 

sufficient for contaminant concentrations to equilibrate 

between the diffusion-sampler water and the pore water in 

the sediments. During retrieval, the membrane of sampler 

WWD-P016 (P16 in fig. 3) was punctured and the sample 

was lost. The scuba divers reported that the bottom 

sediments in the cove were generally fine grained and soft 

except close to the northern shore of the cove and near the 

peninsula. They also reported that the sediments were 

similarly fine grained and soft in the main pond basin 

farther than about 200 ft south of the peninsula.

Table 1. Results of laboratory tests of prototype diffusion samplers 

constructed of tubular cellulose membranes, July 2001

[Analysis by Severn Trent Laboratories, Burlington, Vermont. HMX, 

Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine; No., number; RDX, 

Hexahydro-1,3,5-trinitro-1,3,5-triazine; μg/L, microgram per liter; <, actual 

value is less than value shown]

Well No.

Annulus of test chamber Diffusion sampler

RDX

(μg/L)

HMX

(μg/L)

RDX

(μg/L)

HMX

(μg/L)

MW142M2 <0.25 <0.25 <0.25 <0.25

MW34M1 1.2 <.25 .89 <.25

MW76M2 47 5.7 36 4.6
Field Investigation and Results 7

 64

 65

 66

 67

 54

 55

 56

 57

 58

 59

 60

 61

 62

 63

1

2

3

4

5

6

7

8

9

 10

 11

 12

 13

 14

 15

 16

 17

 18

 19

 20

 21

104 105

 68

 69

 70

 71

 72

 73

106

107

 74

 75

 76

 77

 78

 79

 80

 81

 82

 83

 84

 85

 86

 87

 88

 89

 90

 91

 92

 93

 94

 95

 96

 97

 98

 22

 23

 24

 25

 99

100

 26

 27

 28

 29

 30

 31

 32

 33

 34

 35

 36

 37

 38

101

102

 39

 40

 41

 42

 43

 44

 45

 46

 47

 48

 49

 50

108

103

 51

 52

 53

P2

P3

P4

P5

P6

P7

P8

P9

P10

P11

P12

P13

P14

P15

P16

P17

P18

P19

P20

P21

P22

P23

July 2001 Shoreline Position 

March 2002 

Shoreline Position 

Snake Pond

(altitude on July 3, 2001, 67.2 feet above sea level)

(altitude on March 26, 2002, 65.1 feet above sea level)

826,400

826,800

826,600

281,500 281,700

Base aerial photograph from MassGIS orthophoto, 1 meter resolution, March 1997. 

Massachusetts State Plane Coordinate System Datum is NAD 83 in meters.

0 100 METERS

0 100 200 FEET

50

EXPLANATION

DIFFUSION SAMPLER LOCATION 

AND IDENTIFIER

 37 Sample analyzed

 13 Sample lost or not analyzed

Figure 3. Locations of diffusion samplers set in the bottom sediments of Snake Pond, Cape Cod, Massachusetts, August–October 2001. (Pond altitudes from Rose Forbes, 

Air Force Center for Environmental Excellence, written commun., 2003.)
8 Diffusion and Drive-Point Sampling to Detect Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond, Cape Cod, MA, 2001–02

Table 2. Locations, site identifiers, and installation and retrieval dates of diffusion samplers set in the bottom sediments of Snake Pond, Cape Cod, 

Massachusetts, August–October 2001—Continued

Site

identifier

(fig. 3)

STL control No. USGS sample ID

Distance

from shore

(feet )

Easting

(meters)

Northing

(meters)

Diffusion samplers installed August 24, 2001, and retrieved September 7, 2001

P23 GS08-023 WWD-P023 36 281,633.0 826,799.7

P2 GS08-002 WWD-P002 75 281,634.3 826,787.6

P3 GS08-003 WWD-P003 145 281,632.8 826,766.4

P4 GS08-004 WWD-P004 215 281,631.3 826,745.1

P5 GS08-005 WWD-P005 285 281,629.7 826,723.8

P6 GS08-006 WWD-P006 355 281,628.2 826,702.5

P7 GS08-007 WWD-P007 427 281,626.7 826,680.6

P8 GS08-008 WWD-P008 497 281,625.1 826,659.3

P9 GS08-009 WWD-P009 567 281,623.6 826,638.1

P10 GS08-010 WWD-P010 642 281,622.0 826,615.3

P11 GS08-011 WWD-P011 717 281,620.3 826,592.5

P12 GS08-012 WWD-P012 792 281,618.7 826,569.7

P13 GS08-013 WWD-P013 867 281,617.1 826,546.9

P14 GS08-014 WWD-P014 50 281,611.6 826,511.8

P15 GS08-015 WWD-P015 105 281,610.6 826,495.1

P16 -- WWD-P016 160 281,609.6 826,478.4

P17 GS08-017 WWD-P017 215 281,608.7 826,461.6

P18 GS08-018 WWD-P018 270 281,607.7 826,444.9

P19 GS08-019 WWD-P019 325 281,606.8 826,428.1

P20 GS08-020 WWD-P020 380 281,605.8 826,411.4

P21 GS08-021 WWD-P021 435 281,604.8 826,394.7

P22 GS08-022 WWD-P022 490 281,603.9 826,377.9

-- GS08-024 RDX control from well MW34M1

-- GS08-025 Water blank from deionized water used to fill diffusion samplers

-- GS08-026 Distilled-water control

Diffusion samplers installed September 20-21, 2001, and retrieved October 17, 2001

64 GS11-064 WWD01-0050 50 281,727.3 826,497.9

65 GS11-065 WWD01-0125 125 281,728.1 826,475.1

66 -- WWD01-0200 200 281,728.8 826,452.2

67 GS11-067 WWD01-0275 275 281,729.6 826,429.4

54 -- WWD02-0050 50 281,700.5 826,585.2

55 GS11-055 WWD02-0125 125 281,700.8 826,562.3

56 GS11-056 WWD02-0200 200 281,701.1 826,539.5

57 GS11-057 WWD02-0275 275 281,701.4 826,516.6

58 GS11-058 WWD02-0330 330 281,701.6 826,499.8

59 GS11-059 WWD02-0380 380 281,701.8 826,484.6

Table 2. Locations, site identifiers, and installation and retrieval dates of diffusion samplers set in the bottom sediments of Snake Pond, Cape Cod, 

Massachusetts, August–October 2001

[USGS sample ID: Samples retrieved September 7, 2001, preceded by SNP/RDX/0901. Samples retrieved October 17, 2001, preceded by SNP/RDX/1001. 

State-plane coordinates given as easting and northing, NAD 83. ID, identification number; No., number; RDX, Hexahydro-1,3,5-trinitro-1,3,5-triazine; 

STL, Severn Trent Laboratories; USGS, U.S. Geological Survey; --, sample lost or not analyzed]
Field Investigation and Results 9

Diffusion samplers installed September 20-21, 2001, and retrieved October 17, 2001—Continued

60 GS11-060 WWD02-0430 430 281,702.0 826,469.4

61 GS11-061 WWD02-0480 480 281,702.2 826,454.1

62 -- WWD02-0530 530 281,702.4 826,438.9

63 -- WWD02-0580 580 281,702.6 826,423.6

1 GS11-001 WWD03-0050 50 281,673.3 826,785.0

2 GS11-002 WWD03-0100 100 281,673.1 826,769.8

3 GS11-003 WWD03-0150 150 281,673.0 826,754.5

4 GS11-004 WWD03-0225 225 281,672.7 826,731.7

5 GS11-005 WWD03-0300 300 281,672.4 826,708.8

6 -- WWD03-0375 375 281,672.2 826,686.0

7 GS11-007 WWD03-0450 450 281,671.9 826,663.1

8 GS11-008 WWD03-0525 525 281,671.6 826,640.3

9 GS11-009 WWD03-0600 600 281,671.4 826,617.4

10 GS11-010 WWD03-0675 675 281,671.1 826,594.5

11 GS11-011 WWD03-0750 750 281,670.8 826,571.7

12 GS11-012 WWD03-0825 825 281,670.6 826,548.8

13 -- WWD03-0900 900 281,670.3 826,526.0

14 -- WWD03-0950 950 281,670.1 826,510.7

15 GS11-015 WWD03-1000 1,000 281,669.9 826,495.5

16 GS11-016 WWD03-1050 1,050 281,669.8 826,480.2

17 GS11-017 WWD03-1100 1,100 281,669.6 826,465.0

18 -- WWD03-1150 1,150 281,669.4 826,449.8

19 -- WWD03-1200 1,200 281,669.2 826,434.5

20 -- WWD03-1250 1,250 281,669.1 826,419.3

21 -- WWD03-1300 1,300 281,668.9 826,404.1

104 GS11-104 WWD04-0012 13 281,639.7 826,515.7

105 GS11-105 WWD04-0025 25 281,639.7 826,511.9

68 -- WWD04-0050 50 281,639.6 826,504.9

69 GS11-069 WWD04-0100 100 281,639.5 826,489.7

70 -- WWD04-0150 150 281,639.5 826,474.5

71 GS11-071 WWD04-0200 200 281,639.4 826,459.2

72 GS11-072 WWD04-0250 250 281,639.3 826,444.0

73 GS11-073 WWD04-0300 300 281,639.3 826,428.7

106 GS11-106 WWD05-0012 13 281,602.8 826,527.1

107 GS11-107 WWD05-0025 25 281,602.7 826,523.3

74 GS11-074 WWD05-0050 50 281,602.1 826,516.3

75 GS11-075 WWD05-0100 100 281,601.6 826,501.0

76 GS11-076 WWD05-0150 150 281,601.0 826,485.8

77 GS11-077 WWD05-0200 200 281,600.5 826,470.6

78 GS11-078 WWD05-0250 250 281,600.0 826,455.3

Table 2. Locations, site identifiers, and installation and retrieval dates of diffusion samplers set in the bottom sediments of Snake Pond, Cape Cod, 

Massachusetts, August–October 2001—Continued

Site

identifier

(fig. 3)

STL control No. USGS sample ID

Distance

from shore

(feet )

Easting

(meters)

Northing

(meters)
10 Diffusion and Drive-Point Sampling to Detect Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond, Cape Cod, MA, 2001–02

Diffusion samplers installed September 20-21, 2001, and retrieved October 17, 2001—Continued

79 GS11-079 WWD05-0300 300 281,599.4 826,440.1

80 GS11-080 WWD06-0050 50 281,563.7 826,593.8

81 GS11-081 WWD06-0125 125 281,564.2 826,570.9

82 -- WWD06-0210 210 281,564.8 826,545.0

83 -- WWD06-0250 250 281,565.1 826,532.8

84 GS11-084 WWD06-0300 300 281,565.5 826,517.6

85 GS11-085 WWD06-0350 350 281,565.8 826,502.4

86 GS11-086 WWD06-0400 400 281,566.2 826,487.1

87 -- WWD06-0450 450 281,566.5 826,471.9

88 GS11-088 WWD06-0500 500 281,566.9 826,456.7

89 GS11-089 WWD07-0050 50 281,518.7 826,546.8

90 GS11-090 WWD07-0100 100 281,519.3 826,531.6

91 GS11-091 WWD07-0175 175 281,520.1 826,508.8

92 GS11-092 WWD07-0250 250 281,520.9 826,485.9

93 GS11-093 WWD07-0325 325 281,521.8 826,463.1

94 GS11-094 WWD08-0050 50 281,470.9 826,542.5

95 GS11-095 WWD08-0100 100 281,470.4 826,527.2

96 GS11-096 WWD08-0175 175 281,469.7 826,504.4

97 GS11-097 WWD08-0250 250 281,469.0 826,481.5

98 -- WWD08-0325 325 281,468.2 826,458.7

22 -- WWD09-0050 50 281,697.0 826,750.4

23 GS11-023 WWD09-0125 125 281,696.5 826,727.6

24 GS11-024 WWD09-0200 200 281,696.1 826,704.7

25 -- WWD09-0275 275 281,695.6 826,681.9

99 GS11-099 WWD10-0012 13 281,635.8 826,804.8

100 GS11-100 WWD10-0025 25 281,635.8 826,800.9

26 -- WWD10-0050 50 281,635.9 826,793.6

27 GS11-027 WWD10-0100 100 281,636.1 826,778.3

28 GS11-028 WWD10-0150 150 281,636.3 826,763.1

29 GS11-029 WWD10-0225 225 281,636.6 826,740.2

30 GS11-030 WWD10-0300 300 281,636.9 826,717.4

31 GS11-031 WWD10-0375 375 281,637.2 826,694.5

32 GS11-032 WWD10-0450 450 281,637.5 826,671.7

33 GS11-033 WWD10-0525 525 281,637.8 826,648.8

34 GS11-034 WWD10-0600 600 281,638.0 826,625.9

Table 2. Locations, site identifiers, and installation and retrieval dates of diffusion samplers set in the bottom sediments of Snake Pond, Cape Cod, 

Massachusetts, August–October 2001—Continued

Site

identifier

(fig. 3)

STL control No. USGS sample ID

Distance

from shore

(feet )

Easting

(meters)

Northing

(meters)
Field Investigation and Results 11

Diffusion samplers installed September 20-21, 2001, and retrieved October 17, 2001—Continued

35 GS11-035 WWD10-0675 675 281,638.3 826,603.1

36 GS11-036 WWD10-0750 750 281,638.6 826,580.2

37 GS11-037 WWD10-0825 825 281,638.9 826,557.4

38 GS11-038 WWD10-0890 890 281,639.2 826,537.6

101 GS11-101 WWD11-0012 13 281,597.6 826,805.9

102 GS11-102 WWD11-0025 25 281,597.7 826,802.1

39 GS11-039 WWD11-0050 50 281,597.8 826,795.0

40 GS11-040 WWD11-0100 100 281,598.2 826,779.8

41 GS11-041 WWD11-0150 150 281,598.6 826,764.6

42 GS11-042 WWD11-0225 225 281,599.3 826,741.7

43 GS11-043 WWD11-0300 300 281,599.9 826,718.9

44 GS11-044 WWD11-0375 375 281,600.6 826,696.0

45 GS11-045 WWD11-0450 450 281,601.2 826,673.2

46 GS11-046 WWD11-0525 525 281,601.8 826,650.3

47 GS11-047 WWD11-0600 600 281,602.5 826,627.5

48 GS11-048 WWD11-0675 675 281,603.1 826,604.6

49 GS11-049 WWD11-0750 750 281,603.8 826,581.8

50 -- WWD11-0825 825 281,604.4 826,558.9

108 GS11-108 WWD11-0846 846 281,604.6 826,552.5

103 GS11-103 WWD12-0025 25 281,564.1 826,790.7

51 GS11-051 WWD12-0050 50 281,563.7 826,783.3

52 GS11-052 WWD12-0100 100 281,563.9 826,768.1

53 -- WWD12-0175 175 281,564.2 826,745.2

-- GS11-109 Water blank from deionized water used to fill diffusion samplers

-- GS11-110 Trip blank

-- GS11-111 Snake Pond surface water 281,701.4 826,516.6

Table 2. Locations, site identifiers, and installation and retrieval dates of diffusion samplers set in the bottom sediments of Snake Pond, Cape Cod, 

Massachusetts, August–October 2001—Continued

Site

identifier

(fig. 3)

STL control No. USGS sample ID

Distance

from shore

(feet )

Easting

(meters)

Northing

(meters)

The water samples were analyzed for the 

ordnance-related compounds shown in table 3, except 

for perchlorate, which was not analyzed for in any of the 

diffusion samples. A modification of USEPA method 

8330 (U.S. Environmental Protection Agency, 1994) 

was used that targets various additional explosive 

compounds. The reporting limit for all but three of the 

explosive compounds in water was 0.25 μg/L for a 

500-mL sample volume (table 3).

The samples from the diffusion samplers that were 

buried in the pond-bottom sediments exhibited numerous 

chromatographic peaks. However, an inspection of the 

photo-diode-array (PDA) spectra showed that the peaks 

did not represent the target compounds. The inspections 

were done by comparing the sample spectra to the 

spectra of explosive compounds at known concentrations 

(Elizabeth Wessling, AMEC Earth & Environmental, Inc., 

written commun., 2002). The chromatographic peaks 

probably represent natural organic compounds in the 

pond-bottom sediments. The RDX control sample 

had detectable RDX; there were no detections in the 

distilled-water and water-blank control samples (table 4).
12 Diffusion and Drive-Point Sampling to Detect Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond, Cape Cod, MA, 2001–02

The results from the single transect of samplers 

demonstrated that the diffusion samplers could be 

installed and retrieved in Snake Pond. The analytical data 

did not indicate the presence of explosives at the sampling 

locations. The presence of RDX in the control sample, 

however, confirmed that RDX could diffuse through the 

cellulose membrane if it was present in the water 

surrounding the diffusion sampler.

The single transect of samplers was located along 

the flowpath simulated to pass through the monitoring 

wells on the peninsula in Snake Pond. This alignment 

was a reasonable choice for the first transect because 

there were few other monitoring wells near the pond to 

delineate the width, thickness, and depth of the RDXcontaminated zone. However, ground water originating 

as recharge at the southeastern ranges could discharge at 

locations not crossed by the single transect.

September–October 2001 Transects

On September 20–21, 2001, 12 transects of 108 

diffusion samplers were set in Snake Pond to obtain 

samples from a larger area of the pond bottom (fig. 3) 

than previously sampled. The same methods used for 

the single transect were used to construct, install, and 

retrieve the samplers along the 12 transects. The transects 

extended southward from the northern shore of the cove, 

the southeastern shore of the peninsula, and a swimming 

beach at a youth summer camp. The transects set south of 

the peninsula extended to about 300 ft from shore (fig. 3) 

because ground-water discharge was less likely near the 

center of the pond in areas where the scuba divers had 

reported fine-grained, soft sediments. The diffusion 

samplers were placed at intervals of 12 to 75 ft along 

the transects (table 2).

The diffusion samplers were retrieved on October 

17, 2001, about 27 days after they had been installed. 

These samplers were left in place about twice as long as 

the samplers in the initial transect to provide more time for 

equilibration between contaminant concentrations inside 

and outside of the diffusion samplers and for dissipation 

of the disturbance caused by the installation. The large 

sample volume (500 mL) and potentially low rates of 

ground-water flow through the fine-grained pond-bottom 

sediments at many of the sampled sites could possibly 

increase the equilibration time.

The longer time in the pond-bottom sediments 

described above, however, also resulted in increased 

biodegradation of the cellulose-based diffusion membrane 

(the polyethylene used in earlier studies was not affected 

by biodegradation). Many of the samplers were leaking 

when they were hauled into the boat, particularly the 

samplers that had been buried in the fine-grained, 

organically rich sediments in the center of the cove and in 

the main body of the pond farther than 200 ft from the 

peninsula. The membranes had become so fragile that a 

number of samplers burst and drained completely before 

the water could be decanted into the sample bottles. Other 

samplers leaked rapidly once out of the pond water, and 

less than 500 mL were obtained. Of the intended 108 

diffusion samples, 12 were lost completely and 20 were 

partially lost because of the leaking membranes.

Table 3. Target chemical compounds included in analysis of diffusion and 

drive-point ground-water samples collected beneath Snake Pond, Cape 

Cod, Massachusetts

[Source of information: James Madison, Severn Trent Laboratories, 

Burlington, VT, 2001. HMX, Octahydro-1,3,5,7-tetranitro-1,3,5,7-

tetrazocine; MMR, Massachusetts Military Reservation; PETN, 

Pentaerythritol tetranitrate; RDX, Hexahydro-1,3,5-trinitro-1,3,5-triazine; 

USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per 

liter]

Method Analyte

Reporting

limit

(μg/L)

USEPA 8330 

explosives

HMX 0.25

RDX .25

1,3,5-Trinitrobenzene .25

1,3-Dinitrobenzene .25

Tetryl .25

Nitrobenzene .25

2,4,6-Trinitrotoluene .25

4-amino-2,6-Dinitrotoluene .25

2-amino-4,6-Dinitrotoluene .25

2,6-Dinitrotoluene .25

2,4-Dinitrotoluene .25

2-Nitrotoluene .25

3-Nitrotoluene .25

4-Nitrotoluene .25

MMR-specific 

explosives

2,6-diamino-4-Nitrotoluene .5

2,4-diamino-6-Nitrotoluene .25

Picric acid .25

Nitroglycerin 5

PETN 10

 USEPA 314.0 Perchlorate1 1.5

1Analyzed only for drive-point samples.
Field Investigation and Results 13

Table 4. Validated detections of ordnance-related compounds in diffusion and drive-point samples collected from the pond-bottom sediments of Snake 

Pond, Cape Cod, Massachusetts, August 2001–March 2002

[Analysis by Severn Trent Laboratories, Burlington, VT. Analyte: Photo diode array (PDA) confirmation by AMEC Earth & Environmental, Westford, MA. 

ID, identification number; No., number; RDX, Hexahydro-1,3,5-trinitro-1,3,5-triazine; STL, Severn Trent Laboratories; USGS, U.S. Geological Survey; 

μg/L, micrograms per liter; --, not applicable]

Site identifier

(fig. 4) STL control No. USGS sample ID Date Sample type Analyte Concentration(μg/L)

-- GS08-024 RDX control1 9-07-01 Diffusion RDX 0.66

2 GS11-002 WWD03-0100 10-17-01 Diffusion 2,4-diamino-6-

Nitrotoluene

.35

37 GS11-037 WWD10-0825 10-17-01 Diffusion Nitroglycerin 16

64 GS11-064 WWD01-0050 10-17-01 Diffusion 2,4-diamino-6-

Nitrotoluene

.37

71 GS11-071 WWD04-0200 10-17-01 Diffusion 2-Nitrotoluene 1.1

81 GS11-081 WWD06-0125 10-17-01 Diffusion 2,6-Dinitrotoluene .62

DP5 -- DP0005 12-11-01 Drive point Perchlorate .89

DP9 -- DP0009 3-19-02 Drive point Perchlorate .86

1Water collected from well MW34M1 by AMEC Earth & Environmental, Westford, MA.

To limit the rate of leakage, the samples were 

decanted from the diffusion samplers immediately upon 

being hauled into the boat. No time was taken to rinse off 

the mud and sediments on the outside of the samplers. 

Therefore, some of the water samples decanted into the 

sample bottles were turbid because they had entrained 

sediments that were clinging to the outside of the 

samplers.

The scuba divers reported that 11 samplers were 

completely or partially exposed on the pond bottom. 

Some samplers had been difficult to bury because of hard 

bottom sediments, and other samplers may have become 

exposed because of wave action near the shore. The 

length of time that these samplers were exposed could not 

be determined.

As a result of the lost and completely exposed 

diffusion samplers, water samples from only 88 of the 108 

diffusion samplers were preserved and shipped to the 

laboratory for analysis. The 20 sampling sites that did not 

yield samples are indicated by dashes instead of STL 

control numbers in table 2. The sites that yielded useable 

samples provided good coverage of the sampled area 

(fig. 3).

Once again, three quality-control water samples 

were sent to the laboratory for analysis (table 2). The 

water blank was obtained directly from the deionized 

water supply used to fill the diffusion samplers. The trip 

blank was also obtained directly from the deionized water 

supply, but it was decanted into a sample bottle prior to 

retrieval of the samples and was kept in the sample cooler 

on the boat on the retrieval day. The third sample was 

collected from the Snake Pond surface water near 

diffusion-sampler site 57 (fig. 3).

As in the case of the single transect, the water 

samples from the diffusion samplers exhibited numerous 

chromatographic peaks. However, the PDA inspection of 

the spectra found the target compounds in only five cases 

(table 4). No detections were reported for the pond-water 

sample and the two quality-control samples composed of 

deionized water.

The five sites where target contaminant detections 

were confirmed by the PDA inspection are widely 

scattered and are not related to each other spatially (fig. 4). 

The pond-bottom sediments at the sites varied from sand 

to fine-grained, organically rich sediment. Only one 

compound was detected in each sample, and four different 

compounds were reported for the five sites. These 

compounds are not characteristic of contaminated groundwater samples collected from monitoring wells near the 

Camp Edwards ranges (AMEC, 2002a).
14 Diffusion and Drive-Point Sampling to Detect Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond, Cape Cod, MA, 2001–02

37

81

2

71

64

DP 5,9

July 2001 Shoreline Position 

March 2002 

Shoreline Position 

Snake Pond

(altitude on July 3, 2001, 67.2 feet above sea level)

(altitude on March 26, 2002, 65.1 feet above sea level)

826,400

826,800

826,600

281,500 281,700

Base aerial photograph from MassGIS orthophoto, 1 meter resolution, March 1997. 

Massachusetts State Plane Coordinate System Datum is NAD 83 in meters.

0 100 METERS

0 100 200 FEET

50

EXPLANATION

DIFFUSION-SAMPLING SITE

WITH VALIDATED DETECTION,

AND IDENTIFIER

DIFFUSION-SAMPLING SITE

WITH VALIDATED NON-DETECT

DRIVE-POINT SAMPLING SITE

WITH VALIDATED DETECTION,

AND IDENTIFIER

DRIVE-POINT SAMPLING SITE

WITH VALIDATED NON-DETECT

71

DP 5,9

Figure 4. Locations of validated detections of ordnance-related compounds in diffusion and drive-point water samples collected from bottom sediments of Snake Pond, 

Cape Cod, MA, August 2001–March 2002. (Pond altitudes from Rose Forbes, Air Force Center for Environmental Excellence, written commun., 2003.)
Field Investigation and Results 15

Drive-Point Sampling of Ground Water

The results obtained from the diffusion samplers 

set in the pond-bottom sediments did not indicate an 

area of ground-water discharge containing RDX or other 

explosive compounds. However, the interferences 

in the chromatograms presumed to be caused by natural 

organic compounds resulted in uncertainty concerning 

this conclusion. In addition, the water samples from the 

diffusion samplers were not analyzed for perchlorate. 

This compound had been found in various wells 

upgradient of Snake Pond (AMEC, 2002a) and 

was known to be a propellant used in munitions.

Drive-point sampling was done in December 2001 

and March 2002 to provide confirmation of the diffusionsampler results and to collect ground-water samples under 

the pond for analysis of perchlorate. A total of 21 samples 

were collected at 14 sites (fig. 5 and table 5). The sites 

were selected in areas where the pond bottom was 

sandy because the fine-grained sediments do not yield 

water readily. All but three of the sites were near the 

peninsula because four of the five confirmed detections of 

explosives were obtained from diffusion samplers in this 

general area.

The drive-point samples were collected by 

using a temporary well-point sampler (Macho Model, 

K-V Associates, Inc., Mashpee, MA). The sampler 

consists of threaded 0.63-in.-diameter steel tubing with a 

hardened conical drive point attached at the end. The 

bottom 10 in. of the sampler is slotted vertically to 

allow the entry of pore water. Water samples were 

collected through a 0.1875-in.-outside-diameter flexible 

polyethylene tube inserted inside the sampler opposite the 

slotted screen.

At each sampling site, the depth of the pond 

water was determined by using a folding rule or digital 

fathometer, and the horizontal location was determined by 

using a global positioning system (GPS). The drive point 

was manually driven 2–4 ft below the pond bottom by 

using a sliding hammer so that the point was set in hard 

bottom sediments that presumably were the permeable 

sands and gravels below the soft, poorly permeable 

organically rich sediments. The polyethylene tubing was 

inserted into the sampler, and ground water was 

withdrawn from the tubing by using a peristaltic pump 

fitted with Norprene tubing.

About 1 L was pumped from the sampler prior to 

sample collection to purge the standing water and to 

ensure that representative pore water was being pumped 

from the bottom sediments. The specific conductance of 

the pumped water was measured during the purging and 

was compared to the specific conductance of the pond 

water at the site (table 5). The conductance values 

generally stabilized during the purging process. After 

purging was completed, a 250-mL sample was collected 

in a polyethylene bottle for analysis of perchlorate, and 

two to three 1-L samples were collected in amber glass 

bottles and chilled immediately for analysis of the 

explosive compounds. The sampler was then pulled from 

the sediments and was rinsed with 1–2 L of deionized 

water prior to use at the next sampling site.

The water samples were analyzed for the ordnancerelated compounds listed in table 3, including perchlorate. 

Perchlorate was analyzed by using USEPA method 314.0 

(U.S. Environmental Protection Agency, 1999), which 

was modified to obtain a reporting limit of 1.5 μg/L. The 

explosives samples were analyzed by STL in Burlington, 

VT. Perchlorate was analyzed by Ceimic Corporation in 

Narragansett, RI.

No explosive compounds were detected in the 

ground-water samples collected from the drive points. 

Unlike the water samples obtained from the diffusion 

samplers, there were no chromatographic peaks presumed 

to be caused by natural organic compounds in the bottom 

sediments. The drive point was driven below the 

organically rich sediments and was used to sample ground 

water in the sand and gravel below the bottom sediments.

Perchlorate was detected at sub-μg/L levels 

(table 4) in two drive-point samples collected about 3 

months apart at about the same location (sites DP5 and 

DP9, fig. 4). The pond water was less than 1 ft deep at this 

site on both sampling dates. The specific conductance of 

both samples was equal to the specific conductance of the 

pond water on the respective sampling dates (table 5).
16 Diffusion and Drive-Point Sampling to Detect Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond, Cape Cod, MA, 2001–02

July 2001 Shoreline Position 

March 2002 

Shoreline Position 

Snake Pond

(altitude on July 3, 2001, 67.2 feet above sea level)

(altitude on March 26, 2002, 65.1 feet above sea level)

DP7

DP6

DP5,8,9

DP3

DP4

DP1

DP2

DP10,11

DP12,13

DP14,15

DP16,17 DP18,19

DP20 DP21

826,400

826,800

826,600

281,500

Base aerial photograph from MassGIS orthophoto, 1 meter resolution, March 1997. 

Massachusetts State Plane Coordinate System Datum is NAD 83 in meters.

0 100 METERS

0 100 200 FEET

50

281,700

EXPLANATION

DRIVE-POINT LOCATION 

AND IDENTIFIER

DIFFUSION SAMPLER 

LOCATION

DP7

Figure 5. Locations of temporary drive points installed in the bottom sediments of Snake Pond, Cape Cod, Massachusetts, December 2001 and March 2002. (Pond 

altitudes from Rose Forbes, Air Force Center for Environmental Excellence, written commun., 2003.)
Field Investigation and Results 17

Table 5. Locations, site identifiers, sampling depths and dates, and specific conductance of water samples collected from a temporary well point driven into 

the bottom sediments of Snake Pond, Cape Cod, Massachusetts, December 2001 and March 2002

[USGS sample ID: Samples retrieved December 11, 2001, preceded by SNP/RDX/1201. Samples retrieved March 19, 2002, preceded by SNP/RDX/0302. 

State-plane coordinates given as easting and northing, NAD 83. ID, identification number; USGS, U.S. Geological Survey; μS/cm, microsiemens per 

centimeter at 25°Celsius; --, not applicable]

Site

identifier

(fig. 5)

USGS

sample ID

Easting

(meters)

Northing

(meters)

Water depth

(feet)

Drive distance

below bottom

(feet)

Specific

conductance

(μS/cm)

Samples collected December 11, 2001

DP1 DP0001 281,728.1 826,499.9 1.4 2.6 61

DP2 DP0002 281,700.8 826,517.7 2.3 2.1 96

DP3 DP0003 281,634.4 826,761.3 3.2 2.0 58

DP4 DP0004 281,672.6 826,767.3 2.3 4.0 78

DP5 DP0005 281,635.6 826,542.1 .9 2.2 57

DP6 DP0006 281,636.7 826,474.1 7.8 3.5 61

DP7 DP0007 281,603.4 826,488.5 10.0 2.8 64

-- Pond water -- -- -- -- 57

Samples collected March 19, 2002

DP8 DP0008 281,636.0 826,542.3 0.2 2.0 58

DP9 DP0009 281,636.0 826,542.3 .2 4.0 56

DP10 DP0010 281,621.4 826,549.7 .9 2.0 56

DP11 DP0011 281,621.4 826,549.7 .9 2.0 56

DP12 DP0012 281,648.4 826,534.2 .7 2.0 61

DP13 DP0013 281,648.4 826,534.2 .7 2.0 62

DP14 DP0014 281,661.9 826,517.4 1.4 2.0 65

DP15 DP0015 281,661.9 826,517.4 1.3 2.0 66

DP16 DP0016 281,687.5 826,505.9 .3 2.0 111

DP17 DP0017 281,687.5 826,505.9 .3 2.0 107

DP18 DP0018 281,642.1 826,508.0 1.0 2.0 59

DP19 DP0019 281,642.1 826,508.0 .8 2.0 59

DP20 DP0020 281,662.7 826,484.8 3.3 3.0 60

DP21 DP0021 281,688.7 826,486.7 3.0 2.0 114

-- Pond water -- -- -- -- 56
18 Diffusion and Drive-Point Sampling to Detect Ordnance-Related Compounds in Shallow Ground Water Beneath Snake Pond, Cape Cod, MA, 2001–02

The similarity of the ground-water and pond-water 

values for specific conductance could indicate that pond 

water was being drawn down to the sampling point during 

pumping from the drive-point sampler. A similarity 

between ground-water and pond-water values was 

observed at 16 of the 21 drive-point sampling sites. 

However, the ground-water conductance was substantially 

greater than the pond-water conductance at various sites in 

the northern part of the cove and between the eastern tip of 

the peninsula and the summer-camp swimming beach (for 

example, sites DP16 and DP21, fig. 5 and table 5). The 

drive-point method has been used successfully to sample 

ground water at other sites near Camp Edwards (Savoie 

and others, 2000; McCobb and others, 2003) without 

indication of sample contamination by pond water. The 

similarity of the values could reflect seepage of pond 

water into the aquifer under natural conditions, or could 

result from a coincidental agreement of conductance 

values in pond water and discharging shallow ground 

water in the sampled areas.

ORDNANCE-RELATED COMPOUNDS IN

SHALLOW GROUND WATER BENEATH

SNAKE POND

The diffusion and drive-point sampling was 

performed to determine if ground water containing 

ordnance-related compounds from the southeastern 

ranges at Camp Edwards was discharging to Snake Pond. 

There was concern that discharge could be occurring in 

specific areas at levels that might require prompt action to 

protect human health. Data on the discharge locations 

could also be used to design additional studies of the path 

of contaminants from the ranges, particularly near and 

beneath Snake Pond. Diffusion sampling had been used 

successfully in other ponds near the MMR to locate the 

discharge areas of VOC plumes (Savoie and others, 2000), 

and the use of this method at Snake Pond had the potential 

to provide information on the discharge of ordnancerelated compounds quickly and inexpensively as 

compared to a drilling program on the pond. However, 

the materials used and the sample size were different than 

those of Savoie and others (2000) because the target 

compounds, RDX and other explosives, are not volatile 

compounds.

The results from the diffusion and drive-point 

sampling do not indicate an area of ground-water 

discharge with concentrations of ordnance-related 

compounds and perchlorate that are sufficiently elevated 

to be detected by the sampling methods. The discharge 

may occur in areas that were not sampled. Alternatively, 

the contaminant levels may be too low, either because of 

dispersion in the aquifer or attenuation by dilution, 

sorption, or degradation in the bottom sediments, to be 

detected by the sampling methods. It is also possible that 

the ground water containing the RDX and perchlorate 

detected in monitoring wells north of the pond and on the 

peninsula separating the northern cove from the main 

body of Snake Pond may be deep enough below the water 

table to pass beneath the pond.

Perchlorate was detected in drive-point samples 

on two sampling dates at about the same location on the 

northern shore of the peninsula, but in water with 

the same specific conductance as the pond water. The 

concentrations were less than 1 μg/L. Perchlorate has 

been detected upgradient of Snake Pond, but not in the 

monitoring wells located on the peninsula near the 

drive-point site (AMEC, 2002a). The perchlorate in 

the drive-point samples cannot be linked to perchlorate 

contamination at Camp Edwards with presently (2003) 

available information.

The diffusion and drive-point sampling data cannot 

be interpreted further without additional information 

concerning the pattern of ground-water flow at Snake 

Pond and the distributions of RDX, HMX, and 

perchlorate in the aquifer near the pond. The irregular 

shape and bathymetry of the pond in the simulated area of 

ground-water discharge, including the peninsula that 

becomes smaller or larger or is completely submerged 

depending on the water level, complicate efforts to 

understand the flow directions. Walter and others (2002) 

demonstrated with a ground-water-flow model that 

discharge occurs to the pond in the study area, but the rate 

and location of discharge are affected by the pond-bottom 

characteristics and pumping associated with a nearby 

ground-water-treatment system. Additional model 

simulations could improve the understanding of groundwater flow near Snake Pond and provide a better 

hydrologic framework in which to evaluate water-quality 

data obtained from ground-water sampling by use of 

diffusion samplers, drive points, and monitoring wells.
Summary 19

Additional data delineating the spatial distribution 

of ordnance-related compounds north of Snake Pond and 

beneath the peninsula and shoreline of the pond would 

also help provide a framework for determining where and 

how deep below the pond bottom the contaminants might 

be found. Determining possible discharge locations from 

detections deep in the aquifer and far from the pond is 

highly uncertain, especially if the width and thickness of 

the actual contamination zone upgradient of the pond is 

small. Projecting flowpaths hundreds or thousands of feet 

downgradient from monitoring wells with detections to 

guide the selection of pond-bottom sampling sites is a 

challenging task even when the contaminant plume 

upgradient of the pond is large and reportedly well 

characterized (Savoie and others, 2000).

SUMMARY

Diffusion and drive-point sampling was used by the 

USGS, in cooperation with the Army National Guard 

Bureau, in 2001–02 to determine if ground water 

containing ordnance-related compounds from various 

military ranges at Camp Edwards on the Massachusetts 

Military Reservation was discharging to Snake Pond. The 

diffusion samplers were constructed with cellulose 

membranes that allow diffusion of RDX, HMX, and other 

explosive compounds into the samplers. The 130 

diffusion samplers were buried into the pond-bottom 

sediments by scuba divers along 13 transects and allowed 

to equilibrate with shallow ground water beneath the pond 

for 13-27 days before retrieval. Ground-water samples 

were collected from temporary well points driven into the 

pond bottom at 21 sites and analyzed for explosives and 

perchlorate.

Four explosive compounds were detected in 

diffusion samplers at five widely spaced sites, but the 

detected compounds did not include RDX or MHX and 

generally are not found in the ground water near the 

ranges. Perchlorate was detected at less than 1 μg/L in 

two drive-point samples collected at the same site about 3 

months apart. The results from the diffusion and drivepoint sampling do not indicate an area of ground-water 

discharge with concentrations of ordnance-related 

compounds that are sufficiently elevated to be detected by 

these methods. Additional information from groundwater modeling and sampling on the pattern of groundwater flow at Snake Pond and the distributions of RDX, 

HMX, and perchlorate in ground water in the aquifer near 

the pond would help provide a framework for evaluating 

further the water-quality data obtained from the diffusion 

samplers and drive points. 

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