Toxic Substances Hydrology Program

Comparison of No-Purge and Pumped Sampling

Methods for Monitoring Concentrations of OrdnanceRelated Compounds in Groundwater, Camp Edwards, 

Massachusetts Military Reservation, Cape Cod, 

Massachusetts, 2009–2010

Scientific Investigations Report 2012–5084

U.S. Department of the Interior

U.S. Geological Survey
Cover. View toward the northwest of the Impact Area at Camp Edwards on the Massachusetts Military Reservation, Cape Cod, 

Massachusetts. The pine-barren plant community in the foreground has an open canopy of pitch pine and a dense understory of scrub oak. 

The sand-colored areas near upper left of the photo are excavations associated with the removal of contaminated soil and unexploded 

ordnance. Cape Cod Bay is visible at the upper right of the photo. The photo was taken on April 20, 2012, by the Army National Guard.
Comparison of No-Purge and Pumped 

Sampling Methods for Monitoring 

Concentrations of Ordnance-Related 

Compounds in Groundwater, Camp 

Edwards, Massachusetts Military 

Reservation, Cape Cod, Massachusetts, 

2009–2010

By Jennifer G. Savoie and Denis R. LeBlanc

Toxic Substances Hydrology Program

Prepared in cooperation with the Army National Guard

Scientific Investigations Report 2012–5084

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Savoie, J.G., and LeBlanc, D.R., 2012, Comparison of no-purge and pumped sampling methods for monitoring concentrations of ordnance-related compounds in groundwater, Camp Edwards, Massachusetts Military Reservation, Cape 

Cod, Massachusetts, 2009–2010: U.S. Geological Survey Scientific Investigations Report 2012–5084, 23 p. 

(Also available at http://pubs.usgs.gov/sir/2012/5084.)
iii

Acknowledgments

We thank Aimee Comeau of ECC Environmental, Inc., for her assistance with the selection of the 

monitoring wells, installation of the no-purge sampling devices, and collection of the pumped 

samples; Charles Besse and Rich Bennett of ECC Environmental, Inc., for their assistance in collecting the pumped samples; and Jay Ehret of the U.S. Army Corps of Engineers for his assistance in coordinating the field activities.

We also thank Amanda Cains, Derrick Wagner, and Gillian Fairchild of the U.S. Geological 

Survey for their assistance with the construction, installation, and retrieval of the no-purge 

sampling devices, and Richard Willey of the U.S. Environmental Protection Agency (retired), 

Forest Lyford of the U.S. Geological Survey (retired), Matthew Petkewich of the U.S. Geological Survey, and Benjamin Gregson of the Army National Guard for their helpful comments on 

the manuscript.

v

Contents

Acknowledgments........................................................................................................................................iii

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

Introduction.....................................................................................................................................................1

Groundwater at the Massachusetts Military Reservation ............................................................2

Purpose and Scope ..............................................................................................................................4

Design of Study ..............................................................................................................................................4

Monitoring-Well Selection and Construction ..................................................................................4

Low-Flow Pumped Sampling Method ...............................................................................................4

No-Purge Sampling Methods .............................................................................................................8

Implementation of Field Tests .............................................................................................................8

Laboratory Analysis ..............................................................................................................................9

Comparisons of Concentrations .........................................................................................................9

Comparison of Pumped and No-Purge Sampling Methods ....................................................................9

Comparison of Diffusion and Grab Sampling to Pumped Sampling .............................................9

Vertical Variations of Perchlorate Concentrations in Monitoring-Well Screens .....................12

Comparison of Pumped and Grab Sampling Methods .................................................................14

Collection of Replicate and Large-Volume Samples .....................................................................20

Implications of the Choice of Sampling Methods .........................................................................20

Summary........................................................................................................................................................21

References Cited..........................................................................................................................................22

Figures

 1. Map showing the location of Camp Edwards and the Impact Area at the 
vi

 5. Graphs showing the comparison of concentrations of perchlorate, 

hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7- 

tetranitro-1,3,5,7-tetrazocine (HMX) for concentration ranges of A, 0–120 

and B, 0–20 micrograms per liter for pumped and grab samples collected 

from 29 monitoring wells near the Impact Area on Camp Edwards, Massachusetts 

Military Reservation, Cape Cod, Massachusetts, 2009–2010 ..............................................18

 6. Graphs showing the comparison of concentrations of three ordnance-related 

compounds for concentration ranges of A, 0–120 and B, 0–20 micrograms per liter, 

for pumped and grab samples collected from wells grouped by location relative to 

the altitude of the water table near the Impact Area on Camp Edwards, 

Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010 .................19

 7. Graphs showing the comparison of concentrations of three ordnance-related 

compounds for concentration ranges of A, 0–120 and B, 0–20 micrograms per liter, 

for pumped and grab samples collected from wells grouped by depth of 

screened interval below the water table near the Impact Area on Camp Edwards, 

Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010 .................19

Tables

 1. Location coordinates, land-surface and screened-interval altitudes, depths and 

altitudes of water levels, and well diameters for monitoring wells near the Impact 

Area, Camp Edwards, Massachusetts Military Reservation, 

Cape Cod, Massachusetts ..........................................................................................................5

 2. Field water-quality analyses for water samples collected from monitoring wells 

near the Impact Area by low-flow pumped sampling, Camp Edwards, 

Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010 ...................6

 3. Concentrations of perchlorate and explosive compounds in water samples 

collected from monitoring wells near the Impact Area by using rigid porous 

polyethylene diffusion samplers, regenerated-cellulose membrane diffusion 

samplers, polyethylene-film grab samplers, and low-flow pumped sampling, Camp 

Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 

June–July 2009 ............................................................................................................................10

 4. Concentrations of perchlorate in water samples collected from six monitoring 

wells with 10-foot-long screens near the Impact Area by using low-flow pumped 

sampling and rigid porous polyethylene diffusion samplers, Camp Edwards, 

Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010 .................13

 5. Concentrations of perchlorate and explosive compounds in water samples 

collected from monitoring wells near the Impact Area by using low-flow pumped 

sampling and 1- and 2-liter polyethylene-film grab samplers, Camp Edwards, 

Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010 .................15
vii

Conversion Factors and Datums

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 0.4047 hectare (ha)

Volume

ounce, fluid (fl. oz) 0.02957 liter (L) 

ounce, fluid (fl. oz) 29.57 milliliter (mL)

gallon (gal) 3.785 liter (L) 

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

gallon per minute (gal/min) 3.785 liter per minute (L/min)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Mass

ounce, avoirdupois (oz) 28.35 gram (g) 

Hydraulic conductivity

foot per second (ft/s) 0.3048 meter per second (m/s)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

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

follows: °F=(1.8×°C)+32

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25°C).

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L) or 

micrograms per liter (μg/L).
viii

Abbreviations

AFCEE Air Force Center for Engineering and the Environment

ARNG Army National Guard

ClO4

- perchlorate

EDTA ethylenediaminetetraacetic acid

GRAB1L 1-liter polyethylene-film grab 

GRAB2L 2-liter polyethylene-film grab

HMX octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine

IAGWSP Impact Area Groundwater Study Program

MMR Massachusetts Military Reservation

MWCO molecular weight cutoff

PVC polyvinyl chloride

QA/QC quality assurance and control

RDX hexahydro-1,3,5-trinitro-1,3,5-triazine

RCELLM regenerated-cellulose membrane

RPPOLY rigid porous polyethylene

SPEIM system performance and ecological impact monitoring

USAEC U.S. Army Environmental Command

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

VOC volatile organic compound
Comparison of No-Purge and Pumped Sampling

Methods for Monitoring Concentrations of OrdnanceRelated Compounds in Groundwater, Camp Edwards, 

Massachusetts Military Reservation, Cape Cod, 

Massachusetts, 2009–2010

By Jennifer G. Savoie and Denis R. LeBlanc

Abstract

Field tests were conducted near the Impact Area at 

Camp Edwards on the Massachusetts Military Reservation, Cape Cod, Massachusetts, to determine the utility of 

no-purge groundwater sampling for monitoring concentrations of ordnance-related explosive compounds and perchlorate in the sand and gravel aquifer. The no-purge methods included (1) a diffusion sampler constructed of rigid 

porous polyethylene, (2) a diffusion sampler constructed of 

regenerated-cellulose membrane, and (3) a tubular grab sampler (bailer) constructed of polyethylene film. In samples from 

36 monitoring wells, concentrations of perchlorate (ClO4

- ), 

hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), the major 

contaminants of concern in the Impact Area, in the no-purge 

samples were compared to concentrations of these compounds 

in samples collected by low-flow pumped sampling with 

dedicated bladder pumps. The monitoring wells are constructed of 2- and 2.5-inch-diameter polyvinyl chloride pipe 

and have approximately 5- to 10-foot-long slotted screens. 

The no-purge samplers were left in place for 13–64 days to 

ensure that ambient groundwater flow had flushed the well 

screen and concentrations in the screen represented water in 

the adjacent formation.

The sampling methods were compared first in six 

monitoring wells. Concentrations of ClO4

- , RDX, and HMX 

in water samples collected by the three no-purge sampling 

methods and low-flow pumped sampling were in close agreement for all six monitoring wells. There is no evidence of a 

systematic bias in the concentration differences among the 

methods on the basis of type of sampling device, type of contaminant, or order in which the no-purge samplers were tested. 

A subsequent examination of vertical variations in concentrations of ClO4

-  in the 10-foot-long screens of six wells by using 

rigid porous polyethylene diffusion samplers indicated that 

concentrations in a given well varied by less than 15 percent 

and the small variations were unlikely to affect the utility of 

the various sampling methods.

The grab sampler was selected for additional tests 

in 29 of the 36 monitoring wells used during the study. 

Concentrations of ClO4

- , RDX, HMX, and other minor 

explosive compounds in water samples collected by using 

a 1-liter grab sampler and low-flow pumped sampling were 

in close agreement in field tests in the 29 wells. A statistical 

analysis based on the sign test indicated that there was no bias 

in the concentration differences between the methods. There 

also was no evidence for a systematic bias in concentration 

differences between the methods related to location of the 

monitoring wells laterally or vertically in the groundwaterflow system. Field tests in five wells also demonstrated 

that sample collection by using a 2-liter grab sampler and 

sequential bailing with the 1-liter grab sampler were options 

for obtaining sufficient sample volume for replicate and spiked 

quality assurance and control samples.

The evidence from the field tests supports the conclusion 

that diffusion sampling with the rigid porous polyethylene 

and regenerated-cellulose membranes and grab sampling with 

the polyethylene-film samplers provide comparable data on 

the concentrations of ordnance-related compounds in groundwater at the MMR to that obtained by low-flow pumped 

sampling. These sampling methods are useful methods for 

monitoring these compounds at the MMR and in similar 

hydrogeologic environments. 

Introduction

Groundwater remediation often includes a long-term 

sampling program to monitor the success of the cleanup or the 

fate of contaminants that remain in the aquifer after remediation is completed. The sampling program typically consists of 

collection of groundwater samples from monitoring wells by 
2 Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater

using low-flow, or low-stress, sampling protocols (Puls and 

Barcelona, 1996; U.S. Environmental Protection Agency, 

2010) and portable or dedicated sampling pumps. Low-flow 

sampling can be labor intensive, require expensive sampling 

equipment, and produce excess purge water that must be 

treated before disposal.

No-purge, or passive, sampling methods have been 

developed as a low-cost alternative to low-flow pumped 

sampling (Vroblesky and Hyde, 1997; Parsons, 2005; Interstate Technology & Regulatory Council, 2008). No-purge 

methods are based on the concept that natural flow through 

the well screen (Freeze and Cherry, 1979) results in chemical 

concentrations in the screen that are equal to concentrations 

in the surrounding formation. The no-purge methods use a 

diffusion or grab sampler to obtain a water sample from the 

screened interval without the need to purge the well before 

sampling. Diffusion samplers consist of a diffusion membrane 

filled with a sampling fluid, such as deionized and distilled 

water, that is suspended in the screened interval. After sufficient time has elapsed for concentrations of the chemicals 

of interest to equilibrate across the membrane, the sampler 

is retrieved without the need to pump water from the well. 

Grab samplers consist of a mechanical device that is lowered 

into the screened interval, triggered to capture the water in the 

screen, and retrieved without the need to pump the well. Grab 

samplers collect a sample of the groundwater passing through 

the screen, whereas diffusion samplers use a membrane that 

is permeable to the chemicals of interest so that the chemicals 

can pass into the sampling fluid in the sampler. 

Diffusion samplers are being used for long-term monitoring at sites of groundwater contamination nationwide 

(Parsons, 2005; Interstate Technology & Regulatory Council, 

2008). Most of these applications use a membrane composed of polyethylene film for monitoring volatile organic 

compounds (VOCs). However, the polyethylene film is 

not suitable for monitoring inorganic chemicals or organic 

compounds having higher molecular weights than the VOCs. 

Other membranes that are permeable to these chemicals, such 

as rigid porous polyethylene and regenerated-cellulose, have 

been used at sites where these contaminants are a concern 

(Vroblesky and others, 2002; Parson, 2005). Grab samplers are 

also being used at these sites because they capture the groundwater directly and do not rely on chemical diffusion through a 

permeable membrane. 

Military munitions contain organic and inorganic 

chemicals, such as the high-energy explosive compounds 

hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and the oxidant perchlorate (ClO4

- ). These chemicals, which have been 

detected at levels of concern in groundwater beneath active 

and former military ranges, do not pass through polyethylene 

diffusion membranes. Therefore, monitoring of these chemicals by using no-purge sampling methods would require the 

use of grab samplers or diffusion samplers with other types 

of membranes. Parker and Clark (2004), Parker and Mulherin 

(2007), LeBlanc and Vroblesky (2008), and Parker and others 

(2009) have demonstrated in field and laboratory studies that 

regenerated-cellulose and rigid porous polyethylene diffusion 

samplers and several types of grab samplers can be used to 

obtain groundwater samples from wells for analysis of explosive compounds and perchlorate.

Groundwater at the Massachusetts Military 

Reservation

Long-term monitoring of groundwater quality is a major 

component of groundwater remediation activities at the Massachusetts Military Reservation (MMR), a 22,000-acre multiuse military installation on western Cape Cod, Massachusetts, 

that includes Otis Air National Guard Base and Army National 

Guard Training Area Camp Edwards (fig. 1). The aquifer at 

the MMR consists of glacial deposits of sand and gravel that 

include layers of silt and clay and overlie crystalline bedrock. 

The aquifer is 150–400 feet (ft) thick, is unconfined, and is 

recharged solely by precipitation at an estimated average rate 

of 27 inches per year (in/yr) (Walter and Whealan, 2005). 

The water table on western Cape Cod forms a mound with a 

maximum altitude of about 70 ft near the eastern boundary of 

the MMR (fig. 1). Groundwater flows radially outward from 

the top of the mound toward discharge areas at lakes, streams, 

wetlands, and the coast (LeBlanc and others, 1986; Walter and 

Masterson, 2003; Walter and Whealan, 2005). Groundwater 

flow is predominantly in the horizontal direction, although 

substantial downward and upward flow occurs near the top of 

the water-table mound and near discharge areas.

Groundwater at the MMR is contaminated by a variety 

of chemicals related to military activities that date back to 

the mid-1900s. The contaminants of concern include VOCs, 

ethylene dibromide, ClO4

- , RDX, and HMX. More than two 

dozen plumes of contaminants have been described in the 

aquifer, and several agencies of the Department of Defense 

are actively remediating contaminated soil and groundwater 

on and near the installation (Air Force Center for Engineering 

and the Environment and the U.S. Army Environmental Command, 2010). One area of concern, the Impact Area in Camp 

Edwards, encompasses about 2,200 acres in the northern area 

of the MMR (fig. 1). The contaminants in the Impact Area 

are related to the firing and disposal of military munitions 

and include the ordnance-related explosive compounds RDX 

and HMX and the oxidant ClO4

-  (U.S. Army Environmental 

Command, 2011). These contaminants occur in several plumes 

(fig. 1) that originate from various firing ranges, disposal sites, 

and artillery targets in and near the Impact Area.

Groundwater monitoring at MMR presently (2012) 

includes the quarterly to triennial collection of groundwater samples from more than 1,700 monitoring wells (Rose 

Forbes, Air Force Center for Engineering and the Environment (AFCEE), and Benjamin Gregson, Army National Guard 

Impact Area Groundwater Study Program (IAGWSP), written 

commun., 2012). Monitoring of plumes in the southern part 

of the installation, where VOCs are the main contaminants of 

concern, is done mostly by no-purge diffusion sampling using 
Introduction 3

Figure 1. Location of Camp Edwards and the Impact Area at the Massachusetts Military Reservation, the plumes of ordnance-related 

contaminants, and the monitoring wells that were sampled for this study, as well as the altitude of the water table, western Cape Cod, 

Massachusetts.

55

45

60

65

40

35

30

25

20

15

10

5

25

35

30

40

20

50

65

IMPACT

AREA

MW–89M2

MW–114M1, M2

MW–34M2 MW–481M2

MW–393M1

MW–388M2 MW–368M1, M2

MW–335M1

MW–323M1, M2

MW–313M2

MW–307M3

MW–303M2

MW–293M2

MW–289M2

MW–284M2

MW–279M1

MW–250M2

MW–227M2

MW–211M1

MW–210M1

MW–209M1

MW–207M1

MW–165M2

MW–143M3

MW–142M2

90MW0022

MW–76S, M2

MW–129M1, M2

MW–31S, M

MW–324M2

Areal extent of groundwater contamination—Written 

communication, Installation Restoration Program, 

2008; and Impact Area Groundwater Study Program, 2007

Areal extent of Camp Edwards at the Massachusetts

Military Reservation

Areal extent of Impact Area

Water-table contour—Altitude of water table 

(Walter and Whealan, 2005). Interval is 5 feet. 

Datum NGVD 29

Monitoring well—With identifier MW–34M2

55

Base from the Office of Geographic and Environmental Information (MassGIS),

orthophoto, 1:5000, 2003 Massachusetts state plane projection, 

North American datum 1983

70°32'30’’ 70°30'

41°44'

41°42'

0

0

1 MILE 

1 KILOMETER

EXPLANATION

71°30' 70°00'

42°30'

41°30'

70°00'

BOSTON

Impact

Area 

71°30'

Cape

Cod
4 Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater

polyethylene-membrane samplers and, to a lesser extent, by 

pumped sampling using portable submersible pumps (Rose 

Forbes, AFCEE, written commun., 2012). Archfield and 

LeBlanc (2005) demonstrated that the two sampling methods provided similar VOC concentrations on the basis of 

samples collected from more than 50 monitoring wells near 

the MMR. Monitoring of plumes in and near the Impact Area 

in the northern part of the installation, where RDX, HMX, 

and ClO4

-  are the main contaminants of concern, is done 

primarily by pumped sampling using dedicated submersible 

pumps. In a field study at Camp Edwards in 2004–5, LeBlanc 

and Vroblesky (2008) compared concentrations of ordnancerelated compounds in samples collected by using pumped and 

diffusion sampling methods. They concluded that no-purge 

diffusion sampling was a possible alternative to pumped sampling, although they noted that only 15 wells were sampled 

and only diffusion samplers constructed of rigid porous 

polyethylene were tested in their study. They also reported that 

there was poor agreement between concentrations in the diffusion and pumped samples for 4 of the 15 wells. Those four 

wells were resampled during this study.

Purpose and Scope

This report evaluates the results of field tests of no-purge 

samplers for monitoring concentrations of ClO4

-  and explosive 

compounds in groundwater at Camp Edwards. The field tests 

were conducted in several phases in 2009–2010 in a total of 

36 monitoring wells at Camp Edwards that were known to 

contain various levels of these contaminants. The wells are 

located in various hydrologic settings and have screens set at 

various depths below the water table. Groundwater samples 

were collected by both pumped and no-purge sampling methods, including two types of diffusion samplers and one type of 

grab sampler. The results presented in this report (1) compare 

several alternative methods for the no-purge sampling, 

(2) examine whether hydrologic setting and screen depth 

below the water table affect the degree of agreement between 

concentrations in no-purge and pumped samples, (3) present 

methods for obtaining sufficiently large volumes for quality 

assurance and control samples, and (4) confirm the conclusion presented in LeBlanc and Vroblesky (2008) that no-purge 

sampling may be a useful alternative to pumped sampling. 

This study was done cooperatively by the Toxic Substances 

Hydrology Program of the U.S. Geological Survey (USGS) 

and the Impact Area Groundwater Study Program (IAGWSP) 

of the Army National Guard.

Design of Study

The study included four phases of field tests of the 

no-purge sampling methods in 36 monitoring wells near the 

Impact Area. The wells were installed by the IAGWSP in 

earlier investigations. The field tests included the collection 

of water samples by pumped and no-purge sampling methods 

and laboratory analysis of the samples for concentrations of 

ClO4

- , RDX, HMX, and other explosive compounds. The nopurge sampling methods included diffusion samplers with two 

different types of diffusion membranes and one type of grab 

sampler. The field tests also included the use of diffusion samplers to examine the vertical variations of ClO4

-  concentrations 

in six wells and the use of grab samplers to examine methods 

for obtaining sufficiently large volumes for quality assurance 

and control samples.

Monitoring-Well Selection and Construction

The 36 monitoring wells used during this study are 

sampled annually or semiannually by the IAGWSP. The wells 

were chosen from this regularly sampled set to encompass 

the range of chemical and hydrologic conditions near the 

Impact Area. The selected wells are in the paths of various 

contaminant plumes and are known from historical chemical 

data to include a range of concentrations of ClO4

- , RDX, and 

HMX (nondetectable to about 100, 37, and 10 micrograms 

per liter (μg/L), respectively). The wells are located at various 

positions relative to the top of the water-table mound and, 

therefore, are in areas with gentle to steep horizontal hydraulic gradients. The depths of the wells range from about 18 to 

191 ft below the water table and intercept shallow to deep 

groundwater-flow paths. Four wells (MW–31M, MW–76M2, 

MW–165M2, and MW–289M2) were included in the study in 

order to check the poor agreement between concentrations in 

pumped and diffusion samples from these wells, as reported 

by LeBlanc and Vroblesky (2008) in their study.

The wells are constructed of 2.0- and 2.5-in.-diameter 

polyvinyl chloride (PVC) well casings and slotted screens. 

The wells have about 10-ft-long screens, except for three wells 

that have about 5-ft-long screens (table 1). The wells were 

installed by hollow-stem-auger, dual-casing air-rotary, and 

sonic drilling methods according to the protocols described in 

U.S. Army Environmental Command (2007).

Low-Flow Pumped Sampling Method

The pumped samples were collected by IAGWSP 

contractors and the USGS by using dedicated submersible 

bladder pumps and low-flow sampling methods according to 

the sampling protocols of the U.S. Environmental Protection 

Agency (2010). The average pumping rate was about 0.4 liters 

per minute (L/min), and field water-quality characteristics—

specific conductance, pH, temperature, and dissolved oxygen 

concentration—were monitored for stabilization during the 

purging of each well (table 2). Approximately 3–5 gallons 

(gal) of water were pumped before stabilization was reached 

and samples were collected by the USGS and the IAGWSP 

contractors. This volume is equivalent to about 2–3 times the 

volume of water within the 10-ft-long screened interval of a 

2-in.-diameter well.
Table 1. Location coordinates, land-surface and screened-interval altitudes, depths and altitudes of water levels, and well diameters for monitoring Area, Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts.[Source of data: Impact Area Groundwater Study Program (IAGWSP). Locations shown in figure 1. Altitude in feet relative to National Geodetic Vertical Datum of 1929 (NGVNorth American Datum of 1927 (NAD 27). no., number; ft, feet; mm/dd/yy, month/day/year; in., inch]

Well no.

Northing 

(NAD 27) 

(ft)

Easting 

(NAD 27) 

(ft)

Altitude

of land

surface

(ft)

Altitude of 

top of

screen

(ft)

Altitude of 

bottom of

screen

(ft)

Waterlevel

date 

(mm/dd/yy)

Depth to

water below 

land surface

(ft)

Alti

wat

90MW0022 254100.99 867113.01 105.10 -6.90 -11.90 10/06/09 34.18 7

MW–31M 254181.21 859727.31 153.59 40.59 30.59 10/26/09 85.47 6

MW–31S 254182.23 859727.32 153.59 55.59 50.59 10/26/09 85.48 6

MW–34M2 253831.69 857750.30 144.93 13.93 3.93 06/08/09 78.25 6

MW–76M2 253856.00 858929.99 136.06 31.06 21.06 11/16/09 68.33 6MW–76S 253854.00 858930.01 136.06 51.06 41.06 11/16/09 68.31 6MW–89M2 263731.01 859274.49 207.07 -6.93 -16.93 10/27/09 143.23 6

MW–114M1 253650.41 857818.91 146.73 -30.27 -40.27 06/09/09 79.97 6

MW–114M2 253648.40 857818.91 146.73 26.73 16.73 06/09/09 79.96 6

MW–129M1 253462.51 857861.09 136.25 0.25 -9.75 11/16/09 69.33 6

MW–129M2 253460.51 857861.11 136.25 20.25 10.25 11/16/09 69.32 6

MW–142M2 253946.61 867104.41 112.26 -27.74 -37.74 06/08/09 41.79 7

MW–143M3 254098.59 867130.91 101.83 -5.17 -10.17 10/06/09 30.94 7

MW–165M2 253351.69 856752.01 143.15 18.65 8.65 11/16/09 76.81 6

MW–207M1 266603.61 856491.41 197.74 -56.26 -66.26 10/27/09 140.97 5

MW–209M1 264652.71 857359.79 175.59 -64.41 -74.41 10/27/09 115.35 6

MW–210M1 253222.30 856000.89 161.54 -39.46 -49.46 06/08/09 96.22 6

MW–211M1 252822.49 853901.81 200.14 0.14 -9.86 11/03/09 138.01 6

MW–227M2 253351.09 866864.51 119.29 9.29 -0.71 06/08/09 48.89 7

MW–250M2 252903.00 867073.89 75.84 -69.16 -79.16 06/08/09 4.81 7

MW–279M1 272801.81 853562.53 102.68 6.58 -3.42 10/20/09 70.22 3

MW–284M2 275132.89 851430.84 28.40 -16.60 -26.60 11/03/09 22.62 

MW–289M2 259281.08 868635.02 169.18 6.84 -3.16 10/06/09 98.51 7

MW–293M2 261216.15 868890.36 173.80 -23.12 -33.12 10/06/09 104.40 6

MW–303M2 258625.31 866413.09 180.79 -54.30 -64.31 10/20/09 109.83 7

MW–307M3 257560.60 869226.64 172.86 47.06 37.04 09/22/09 102.27 7

MW–313M2 263374.95 870040.63 186.42 -29.04 -39.07 10/14/09 119.29 6

MW–323M1 271899.40 853422.00 109.56 -85.44 -95.44 10/20/09 72.07 3

MW–323M2 271898.61 853421.99 109.56 -10.44 -20.44 10/20/09 72.05 3

MW–324M2 258966.00 871733.68 174.08 -29.66 -40.66 10/06/09 104.22 6

MW–335M1 259607.84 871192.56 177.52 -77.68 -87.68 09/22/09 107.70 6

MW–368M1 258680.41 871017.69 171.43 -64.57 -74.57 09/22/09 101.93 6

MW–368M2 258680.57 871017.69 171.43 -31.57 -41.57 09/22/09 101.72 6

MW–388M2 258727.57 869639.90 140.91 -3.84 -13.84 10/06/09 70.18 7

MW–393M1 260721.56 872166.01 156.51 -112.05 -122.05 09/21/09 87.99 6

MW–481M2 254052.88 870108.69 156.16 9.88 -0.12 10/27/09 85.24 7
6 Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater

Table 2. Field water-quality analyses for water samples collected from monitoring wells near the Impact Area by low-flow pumped 

sampling, Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010.

[Source of data: U.S. Geological Survey. Locations shown in figure 1. no., number; --, not analyzed; mm/dd/yy, month/day/year; °C, degrees Celsius; μS/cm, 

microsiemens per centimeter at 25 degrees Celsius; mg/L, milligram per liter]

Well no.

Sample 

date 

(mm/dd/yy)

Temperature

(°C)

Specific

conductance

(μS/cm)

pH

(standard

units)

Dissolved

oxygen

(mg/L)

90MW0022 10/06/09 11.6 78.4 5.83 2.9

MW–31M 11/18/09 11.1 84.3 5.77 11.5

MW–31S 11/18/09 10.7 120.7 5.49 9.8

MW–31S 09/01/10 14.2 99.5 5.41 8.4

MW–34M2 06/08/09 10.9 51.5 5.99 11.5

MW–34M2 07/20/09 11.6 52.7 5.92 11.4

MW–76M2 11/16/09 10.4 98.1 5.73 10.3

MW–76M2 09/01/10 11.4 81.5 5.62 10.7

MW–76S 11/16/09 10.6 55.3 5.97 11.8

MW–89M2 10/27/09 10.8 57.1 6.43 11.7

MW–89M2 09/01/10 14.3 43.3 6.28 11.0

MW–114M1 06/09/09 11.3 51.6 6.28 11.8

MW–114M1 07/21/09 13.1 51.2 6.25 12.2

MW–114M2 06/09/09 11.1 52.3 5.96 11.8

MW–114M2 07/21/09 11.4 52.5 5.97 11.9

MW–129M1 06/09/09 10.4 50.7 6.12 11.8

MW–129M1 06/23/09 10.6 50.9 -- 11.9

MW–129M1 11/16/09 10.8 49.8 6.15 11.7

MW–129M2 06/09/09 10.4 52.0 5.98 11.9

MW–129M2 06/23/09 10.9 52.1 6.01 12.2

MW–129M2 11/16/09 10.4 51.1 6.06 11.6

MW–142M2 06/08/09 12.0 74.1 5.76 9.7

MW–142M2 06/23/09 11.3 74.5 5.78 10.3

MW–143M3 10/06/09 10.4 71.1 5.78 10.3

MW–165M2 11/16/09 10.1 53.2 6.07 11.6

MW–207M1 10/27/09 10.5 58.1 6.81 11.6

MW–209M1 10/27/09 10.4 49.3 6.51 11.7

MW–210M1 06/08/09 11.3 61.5 6.62 11.1

MW–210M1 07/20/09 12.4 64.4 6.62 11.3
Design of Study 7

Table 2. Field water-quality analyses for water samples collected from monitoring wells near the Impact Area by low-flow pumped 

sampling, Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010.—Continued

Well no.

Sample 

date 

(mm/dd/yy)

Temperature

(°C)

Specific

conductance

(μS/cm)

pH

(standard

units)

Dissolved

oxygen

(mg/L)

MW–211M1 11/18/09 11.1 51.7 6.29 12.1

MW–211M1 09/02/10 16.9 51.2 6.49 11.5

MW–227M2 06/08/09 11.0 66.4 5.91 9.8

MW–227M2 07/20/09 11.8 64.3 5.92 11.3

MW–250M2 06/08/09 10.6 84.4 6.05 10.0

MW–250M2 07/20/09 11.8 83.1 6.07 9.8

MW–279M2 10/20/09 10.4 70.8 6.45 11.0

MW–284M2 11/03/09 11.3 103.1 6.03 10.2

MW–289M2 10/06/09 11.0 55.4 6.04 11.2

MW–293-M2 10/06/09 10.8 59.4 6.23 12.0

MW–303M2 10/21/09 12.0 53.0 6.08 6.9

MW–303M2 09/01/10 13.7 45.5 5.97 8.0

MW–307M3 09/22/09 13.0 47.2 5.87 12.2

MW–313M2 10/13/09 10.6 55.1 6.49 11.8

MW–323M1 10/20/09 11.3 68.8 6.10 7.9

MW–323M2 10/20/09 10.7 54.4 6.07 10.9

MW–323M2 09/02/10 14.4 53.5 6.04 11.6

MW–324M2 10/06/09 11.3 63.7 6.67 10.9

MW–335M1 09/22/09 11.3 56.9 6.55 8.6

MW–368M1 09/22/09 12.1 59.2 6.90 8.7

MW–368M1 09/02/10 14.7 60.0 6.96 8.8

MW–368M2 09/22/09 12.2 76.0 7.11 9.0

MW–368M2 09/02/10 13.5 80.1 7.06 10.0

MW–388M2 10/06/09 11.0 54.3 6.17 11.5

MW–393M1 10/13/09 9.7 68.6 7.22 12.0

MW–481M2 10/27/09 10.8 72.7 6.13 11.1
8 Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater

No-Purge Sampling Methods

Three types of no-purge samplers were tested in this 

study: (1) diffusion samplers constructed of rigid porous 

polyethylene (RPPOLY) membranes, (2) diffusion samplers 

constructed of regenerated-cellulose (RCELLM) membranes, and (3) two sizes—1 liter (L) (GRAB1L) and 2 L 

(GRAB2L)—of disposable polyethylene-film grab samplers.

The RPPOLY samplers were constructed of rigid, 

porous polyethylene tubing as described in LeBlanc and 

Vroblesky (2008). RPPOLY samplers are available commercially (Columbia Analytical Services, 2012); for this study, 

however, the samplers from the 2004–5 study by LeBlanc 

and Vroblesky (2008) were reused after being soaked and 

rinsed thoroughly with deionized water. Each sampler holds 

about 160 milliliters (mL) of deionized water. Therefore, 

four RPPOLY samplers were used in each well to obtain the 

625 mL of water required for chemical analysis. The samplers 

were suspended in the well on polypropylene line and spaced 

evenly along the length of the 10-ft-long well screen. After 

retrieval of the samplers, the water from all four samplers was 

decanted into a 1-L amber-colored glass bottle. About 125 mL 

was then decanted from the blended sample into a polyethylene bottle for analysis of ClO4

- . The water remaining in the 

1-L glass bottle was used for analysis of explosive compounds. 

The RCELLM samplers were constructed of high-grade 

regenerated-cellulose tubular dialysis membrane. The membrane was 50 millimeters (mm) wide when lying flat and had 

a nominal molecular-weight cutoff (MWCO) of 8,000 daltons. 

The membrane is packed for shipping in a storage solution 

of ethanol, sodium benzoate, and ethylenediaminetetraacetic 

acid (EDTA) and must be rinsed thoroughly with deionized 

water before use. To construct the samplers, the membrane 

was cut to working lengths of about 40 in. and rinsed five 

times with deionized water. A knot was tied at one end of the 

tubular membrane, the tube was filled with about 480 mL of 

deionized water, and a knot was tied at the other end to close 

the tube. The water-filled tube, which was about 24 in. long, 

was then slid into a flexible nylon-mesh tube for protection. Two RCELLM samplers were suspended in the well 

on polypropylene line, with one sampler set directly above 

and the other set directly below the midpoint of the screened 

interval. After retrieval of the samplers, the water from the two 

samplers was decanted into a 1-L amber-colored glass bottle. 

About 125 mL was then decanted from the blended sample 

into a polyethylene bottle for analysis of ClO4

- . The water 

remaining in the 1-L glass bottle was used for analysis of 

explosive compounds.

The grab samplers are tubular disposable bailers constructed of 4-mil-thick (4 thousandths of an inch) polyethylene 

film with a polyethylene check valve at the top of the sampler 

(GeoInsight, 2012a, b). Two sizes of grab samplers were used 

in the study. The smaller (HydraSleeve GRAB1L) samplers 

(model no. HS-2-1L) were 36 in. long and had a diameter 

of 1.6 in. and a volume of about 1 L when filled. The larger 

(SuperSleeve GRAB2L) samplers (model no. HSSS-2L) were 

60 in. long and had a diameter of 1.6 in. and a volume of about 

2 L when filled. Only one sampler was needed per well to 

obtain sufficient volume for laboratory analysis.

The smaller GRAB1L samplers were deployed in wells 

with 10-ft-long screens by setting the check valve, attaching a 

stainless-steel weight to the bottom of the sampler, and lowering the sampler on a polypropylene line into the well until 

the weight rested on the bottom and, as a result, the top, open 

end of the sampler was about 3 ft below the midpoint of the 

screened interval. In wells with 5-ft-long screens, a stainlesssteel weight was also attached to the top of the sampler. This 

upper weight caused the top of the sampler to rest near the 

bottom of the well and below the screened interval. To fill the 

sampler with water from the screened interval before retrieval 

from the wells with the 10-ft-long screens, the polypropylene 

line was pulled up in one continuous 5-ft-long stroke at a rate 

of about 1–2 feet per second (ft/s). In wells with 5-ft-long 

screens, two shorter strokes were used, and the sampler was 

allowed to settle to the bottom of the well between strokes. 

The filled sampler was raised to the surface at a steady rate of 

1–2 ft/s.

The larger GRAB2L samplers were deployed only in 

wells with 10-ft-long screens. Stainless-steel weights were 

attached to the top and bottom of the sampler so that it rested 

on the bottom of the well when deployed. To fill the sampler 

with water from the screened interval, the polypropylene line 

was pulled up in two continuous 5-ft-long strokes at a rate of 

about 1–2 ft/s. The sampler was allowed to settle to the bottom of the well between the strokes, and it was raised to the 

surface at a rate of about 1–2 ft/s.

The water from the GRAB1L and GRAB2L samplers 

was decanted directly into either 500-mL or 1-L amber-glass 

bottles for analysis of explosive compounds and 125-mL polyethylene bottles for analysis of ClO4

- . Blending of the sample 

in a 1-L bottle, as was done for the RPPOLY and RCELLM 

samples, was not necessary because one grab sample yielded 

sufficient water for the chemical analyses.

Implementation of Field Tests

The field tests were conducted in four phases to (1) compare pumped sampling and several types of no-purge sampling 

in a smaller number of wells, (2) determine whether vertical 

variations in concentrations along the screened interval are 

present that could affect the sampling results, (3) compare 

pumped and one type of no-purge sampling in a larger number 

of wells, and (4) test several methods for obtaining larger 

sample volumes from the no-purge samplers for use in quality 

assurance and control evaluation. These phases are described 

in detail in the next section of this report.

Field tests during the first phase of the study began 

with the collection of water samples by using the dedicated 

sampling pumps, which were already in place in the wells. 

During all four phases of the study, the pumps were then 
Comparison of Pumped and No-Purge Sampling Methods 9

removed from the wells and stored in plastic bags, and the 

no-purge samplers were set in the wells as described above. 

The no-purge samplers, including the grab samplers, remained 

in the wells for 13–64 days before their retrieval to ensure that 

ambient flow through the well screen had flushed the screened 

interval after setting of the sampler and, therefore, that the 

water in the screen represented the water in the adjacent formation. The 13-day or longer time interval also allowed ample 

time for equilibration of contaminant concentrations between 

the groundwater in the screen and the deionized water inside 

the RPPOLY and RCELLM diffusion samplers (Vroblesky, 

2001; LeBlanc, 2003). After collection of the no-purge 

samplers, the pumps were reinstalled in the wells and used to 

collect pumped samples about 2–24 hours later; this short time 

lag allowed sediment that had been resuspended into the water 

column during retrieval of the samplers and reinstallation of 

the pump to settle back to the bottom of the well.

Laboratory Analysis

Water samples for analysis of the explosive compounds 

were collected in 500-mL or 1-L amber-glass bottles, chilled 

immediately, and stored chilled until analysis. Samples for 

analysis of ClO4

-  were collected in 125-mL polyethylene 

bottles and stored in the dark at room temperature until analysis. The explosive compounds were analyzed by U.S. Environmental Protection Agency (USEPA) method 8830A (U.S. 

Environmental Protection Agency, 2008), and the ClO4

-  samples were analyzed by USEPA method 314.0 (U.S. Environmental Protection Agency, 1999). The samples were analyzed 

by laboratories under contract to the USGS. The reporting and 

detection limits vary with sample volume and magnitude of 

measured concentration; the reporting limits for ClO4

- , RDX, 

and HMX were about 1.0, 0.2, and 0.4 μg/L, respectively; the 

detection limits for ClO4

- , RDX, and HMX were about 0.25, 

0.06, and 0.10 μg/L, respectively. Concentrations between the 

reporting and detection limits are considered estimated values. 

The compounds that are measured by USEPA method 8830A 

are shown in LeBlanc and Vroblesky (2008, table 2). Only 

compounds for which at least one sample had a concentration 

exceeding the detection limit of the compound are included in 

the tables in this report.

Comparisons of Concentrations

The small sample sizes for most sets of comparisons 

between the no-purge and pumped sampling results precluded the use of formal statistical comparisons, except as 

part of the fourth phase of work, in which grab and pumped 

sampling methods were compared in 29 wells. For most 

comparisons, the degree of agreement between methods is 

assessed qualitatively by using bar graphs and scatter plots. 

Methods are described as showing a close agreement when, 

for example, the data points in a scatter plot are, by visual 

inspection, close to, and randomly scattered about, the line of 

equal concentration. Other quantitative measures of the degree 

of agreement, such as percent differences or absolute differences between concentrations, can be misleading when applied 

over a large range of concentration values and, therefore, were 

not used in this study.

Comparison of Pumped and No-Purge 

Sampling Methods

The comparison of pumped and no-purge sampling methods for monitoring ordnance-related compounds at the MMR 

was conducted in several phases in a total of 36 wells; several 

wells were used in more than one phase of the study. During 

the first phase, two types of diffusion samplers and one type of 

grab sampler were compared to low-flow pumped sampling in 

six monitoring wells. In the second phase, RPPOLY samplers 

were used in six monitoring wells to test whether vertical 

variations in chemical concentrations that could affect the performance of the no-purge sampling methods were present in 

the screened intervals of the wells. The grab-sampler no-purge 

sampling method was compared to low-flow pumped sampling 

in 29 wells in the third phase of the study to obtain sufficient 

data for a statistical as well as graphical comparison of the 

methods and to test whether well location and construction 

affected the degree of agreement between the two methods. 

During the fourth phase of the study, several grab sampling 

approaches for collecting sufficiently large volumes for quality 

control and assurance samples were tested in five wells.

The comparisons among the sampling methods focus on 

concentrations of ordnance-related compounds and especially 

those of most concern at the MMR—ClO4

- , RDX, and HMX. 

Water-quality measurements were made in the field during 

collection of the pumped samples (table 2). The groundwater 

at all the wells sampled during this study had a low dissolved 

solids content (specific conductance of 43.3–120.7 microsiemens per centimeter) and was aerobic (dissolved oxygen 

concentrations of 2.9–10.7 milligrams per liter) and generally 

mildly acid (pH of 5.41–7.22).

Comparison of Diffusion and Grab Sampling to 

Pumped Sampling

In the first phase of the study, concentrations of ClO4

- 

, 

RDX, HMX, and other minor explosive compounds in water 

samples collected by using RPPOLY and RCELLM diffusion 

sampling and GRAB1L grab sampling were compared to concentrations of these compounds in samples collected by using 

low-flow pumped sampling in six wells (table 3). At each 

well, the no-purge samplers were set sequentially following 

collection of the initial pumped sample. Each type of diffusion 

and grab sampler was left in the well for 13–15 days. The final 

pumped sample was collected within 24 hours of retrieval of 

the last no-purge sampler. The order of testing of the no-purge 
10 Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater

Table 3. Concentrations of perchlorate and explosive compounds in water samples collected from monitoring wells near the Impact 

Area by using rigid porous polyethylene diffusion samplers, regenerated-cellulose membrane diffusion samplers, polyethylene-film 

grab samplers, and low-flow pumped sampling, Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 

June–July 2009.

[Samples analyzed by Test America, Arvada, Colo. Sample designation: Well number in tables 1–2 and suffix; PUMPED, low-flow pumped; RCELLM, 

regenerated-cellulose membrane; RPPOLY, rigid porous polyethylene; GRAB1L, 1-liter polyethylene-film grab. Locations shown in fig. 1. mm/dd/yy, month/

day/year; μg/L, microgram per liter; HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine; RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine; WATERBLANK, 

deionized water used to fill RPPOLY and RCELLM samplers; <, less than value shown; E, estimated value]

Sample designation

Sample 

date 

(mm/dd/yy)

Perchlorate

(μg/L)

HMX

(μg/L)

RDX

(μg/L)

4-Amino-2,6-

dinitrotoluene

(μg/L)

MW–34M2-PUMPED 06/08/09 1.4 <0.40 <0.20 <0.20

MW–34M2-RCELLM 06/22/09 1.0 <0.40 <0.20 <0.20

MW–34M2-RPPOLY 07/07/09 1.1 <0.40 <0.20 <0.20

MW–34M2-GRAB1L 07/20/09 1.0 <0.40 <0.20 <0.20

MW–34M2-PUMPED 07/20/09 2.0 <0.40 <0.20 <0.20

MW–114M1-PUMPED 06/09/09 4.8 E 0.23 3.5 <0.20

MW–114M1-RPPOLY 06/23/09 3.7 E 0.21 3.9 <0.20

MW–114M1-GRAB1L 07/07/09 5.6 E 0.25 3.3 <0.20

MW–114M1-RCELLM 07/20/09 5.3 E 0.21 3.4 <0.20

MW–114M1-PUMPED 07/21/09 4.0 E 0.19 2.9 <0.20

MW–114M2-PUMPED 06/09/09 2.1 E 0.18 0.44 <0.20

MW–114M2-RPPOLY 06/23/09 1.7 E 0.10 <0.20 <0.20

MW–114M2-GRAB1L 07/07/09 2.0 <0.40 <0.20 E 0.13

MW–114M2-RCELLM 07/20/09 2.6 <0.40 E 0.12 <0.20

MW–114M2-PUMPED 07/21/09 2.4 E 0.28 0.59 <0.20

MW–210M1-PUMPED 06/08/09 1.5 <0.40 0.22 <0.20

MW–210M1-RCELLM 06/22/09 E 0.90 <0.40 <0.20 <0.20

MW–210M1-RPPOLY 07/07/09 1.5 <0.40 <0.20 <0.20

MW–210M1-GRAB1L 07/20/09 1.4 <0.40 E 0.08 <0.20

MW–210M1-PUMPED 07/20/09 E 0.94 <0.40 E 0.14 <0.20

MW–227M2-PUMPED 06/08/09 E 0.94 2.6 28 <0.20

MW–227M2-GRAB1L 06/22/09 E 0.77 2.6 28 <0.20

MW–227M2-RCELLM 07/07/09 E 0.82 2.4 24 <0.20

MW–227M2-RPPOLY 07/20/09 E 0.82 2.8 19 <0.20

MW–227M2-PUMPED 07/20/09 E 0.96 2.9 24 <0.20

MW–250M2-PUMPED 06/08/09 8.2 <0.40 1.5 <0.20

MW–250M2-GRAB1L 06/23/09 6.6 <0.40 1.5 <0.20

MW–250M2-RCELLM 07/07/09 7.4 <0.40 1.9 <0.20

MW–250M2-RPPOLY 07/20/09 6.4 <0.40 1.4 <0.20

MW–250M2-PUMPED 07/20/09 7.2 <0.40 1.5 <0.20

WATERBLANK 06/08/09 <1.0 <0.40 <0.20 <0.20
Comparison of Pumped and No-Purge Sampling Methods 11

samplers was varied among the wells to limit any potential 

bias owing to the sampling order. 

The compounds of interest were not detected in a sample 

of the deionized water that was used to fill the RPPOLY and 

RCELLM samplers (water blank, table 3). In this study, blank 

samples were not collected from no-purge samplers set in 

chambers filled with water known to be free of the compounds 

of concern. Similar tests in earlier studies (LeBlanc, 2003; 

LeBlanc and Vroblesky, 2008) had not detected any contamination from the samplers themselves, including RPPOLY 

samplers that had been reused after soaking and rinsing with 

deionized water. 

The concentrations of ClO4

- , RDX, and HMX in the nopurge and pumped samples collected from the six monitoring 

wells were in close agreement, as is evident qualitatively in 

bar graphs that compare the concentrations (fig. 2). There is no 

evidence of a systematic bias in the concentration differences 

on the basis of type of sampling device or type of contaminant. There is also no evidence of a systematic bias on the 

basis of the order in which the no-purge samplers were tested 

Figure 2. Comparison of perchlorate, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine 

(HMX) concentrations for pumped, diffusion, and grab samples collected from six monitoring wells near the Impact Area on Camp 

Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009. Concentrations include estimated values (identified 

in table 3) and are plotted as zero values where less than the detection limit. Pumped-1, initial low-flow pumped sample; RPPOLY, rigid 

porous polyethylene diffusion sample; RCELLM, regenerated-cellulose membrane diffusion sample; GRAB1L, 1-liter polyethylene-film 

grab sample; Pumped-2, final low-flow pumped sample.

Pumped-1

RPPOLY

GRAB1L

RCELLM

Pumped-2

Pumped-1

RPPOLY

GRAB1L

RCELLM

Pumped-2

Pumped-1

RCELLM

RPPOLY

GRAB1L

Pumped-2

Pumped-1

GRAB1L

RCELLM

RPPOLY

Pumped-2

Pumped-1

GRAB1L

RCELLM

RPPOLY

Pumped-2

Pumped-1

RCELLM

RPPOLY

GRAB1L

Pumped-2

0

2

4

6

8

10

0

2

4

6

8

10

0

2

4

6

8

10

0

10

20

30

0

2

4

6

8

10

Perchlorate HMX RDX

Perchlorate HMX RDX

Perchlorate HMX RDX

0

2

4

6

8

10

Perchlorate HMX RDX

Perchlorate HMX RDX

Perchlorate HMX RDX

Concentration, in micrograms 

per liter

Concentration, in micrograms 

per liter

Concentration, in micrograms 

per liter

MW–114M1 MW–114M2

MW–210M1 MW–227M2

MW–250M2 MW–34M2

EXPLANATION

EXPLANATION

EXPLANATION

EXPLANATION

EXPLANATION

EXPLANATION
12 Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater

(fig. 2, table 3). The concentrations are also in close agreement 

over the range of observed values for ClO4

- , RDX, and HMX 

(fig. 3). RDX and HMX were detected at low concentrations 

(less than 0.6 μg/L) in more pumped than no-purge samples, 

but the concentrations are near the detection limits for the 

compounds. ClO4

-  was detected in all the pumped and nopurge samples.

Vertical Variations of Perchlorate 

Concentrations in Monitoring-Well Screens

The second phase of the project examined whether vertical variations in contaminant concentrations were present in 

the well screens. The diffusion and grab sampling methods 

differ in the vertical position and number of devices set within 

the well screen. The diffusion samplers do not remove water 

from the screened interval, whereas the grab sampler scoops 

up water from the screened interval. The pumped sampling 

method draws water from the formation, but the contributions 

to the pumped sample from various intervals along the screen 

are unknown and thus may conceal vertical variations in concentrations and hydraulic properties along the screen.

Concentrations of contaminants can vary considerably 

over long screened intervals (Reilly and LeBlanc, 1998), and 

fluid can circulate vertically inside long screens and even in 

the blank casing above the screen during and between sampling events (Church and Granato, 1996; Vroblesky and others, 2007). The degree of agreement between sampling methods, which differ in where and how the samples are collected, 

could be affected by these factors. The close agreement among 

concentrations of ClO4

- , RDX, and HMX in the no-purge and 

pumped samples collected from the six monitoring wells in the 

first phase of the study, in which the three no-purge sampling 

methods were tested, suggests that variations in concentrations 

over the screened intervals were small, but these data were not 

sufficient to confirm this hypothesis or quantify the variability.

To examine whether the close agreement among concentrations could be due partly to uniform concentrations 

in the screened intervals, variations in concentrations of 

ClO4

-  were measured by using RPPOLY diffusion samplers 

in six wells. Only variations in ClO4

-  concentrations were 

examined because each RPPOLY sampler did not contain a 

sufficient sample volume for analysis of explosive compounds 

(500 mL). In three of the six wells, four RPPOLY samplers 

were placed at about 2, 4, 6, and 8 ft below the top of the 

10-ft-long screen (table 4). Pumped samples were collected 

before and after collection of the RPPOLY samplers. In the 

other three wells, in addition to the four samplers in the 

Figure 3. Comparison of perchlorate, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine 

(HMX) concentrations for pumped and no-purge samples collected from six monitoring wells near the Impact Area on Camp Edwards, 

Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009, for concentration ranges of A, 0 –30 and B, 0–10 micrograms per 

liter. Concentrations include estimated values (identified in table 3) and are plotted as zero values where less than the detection limit.

EXPLANATION

0

5

10

15

20

25

30

0 5 10 15 20 25 30

Line of equal concentrations

A

0

2

4

6

8

10

0 2 4 6 8 10

RDX

HMX

Perchlorate

Line of equal concentrations

B

No-purge sample concentration, in micrograms per literNo-purge sample concentration, in micrograms per liter

Pumped sample concentration, in micrograms per liter Pumped sample concentration, in micrograms per liter
Comparison of Pumped and No-Purge Sampling Methods 13

screened interval, RPPOLY samplers were placed in the blank 

casing above the well screen at about 0, 2, 4, and 6 ft above 

the top of the screen. Pumped samples were collected from 

these wells only after collection of the RPPOLY samplers.

Small variations in concentrations of ClO4

-  over the sampled interval were measured in all six wells (table 4, fig. 4), 

but the individual sample concentrations in a given well generally differed by less than 15 percent from the average concentration of the four or eight samples in the well. For the 6 out of 

36 samples with relative differences greater than 15 percent, 

the absolute differences were less than 2 μg/L. The largest 

deviations from the average concentration were in the bottom 

sample in the three wells with the highest average concentrations. The ClO4

-  concentrations in the pumped samples were 

in close agreement with the average concentrations in the 

RPPOLY samples, with the exception of the pumped sample 

from well MW–368M2. The cause for this anomalously large 

difference is not known.

Table 4. Concentrations of perchlorate in water samples collected from six monitoring wells with 10-foot-long screens near the Impact 

Area by using low-flow pumped sampling and rigid porous polyethylene diffusion samplers, Camp Edwards, Massachusetts Military 

Reservation, Cape Cod, Massachusetts, 2009–2010.

[Samples analyzed by Test America, Arvada, Colo. Locations shown in figure 1. Sample designation: Pumped, low-flow pumped sample; xx ft, depth below top 

of screen of rigid porous polyethelene sampler. no., number; mm/dd/yy, month/day/year; μg/L, microgram per liter; E, estimated value; ft, foot].

Well no. Sample 

designation

Sample 

date 

(mm/dd/yy)

Perchlorate

(μg/L)

MW–129M1 Pumped 06/09/09 1.1

MW–129M1 2.5 ft 06/23/09 3.0

MW–129M1 4.1 ft 06/23/09 2.6

MW–129M1 5.8 ft 06/23/09 3.0

MW–129M1 7.5 ft 06/23/09 3.5

MW–129M1 Pumped 06/23/09 1.6

MW–129M2 Pumped 06/09/09 1.8

MW–129M2 2.5 ft 06/23/09 2.6

MW–129M2 4.1 ft 06/23/09 2.0

MW–129M2 5.8 ft 06/23/09 1.5

MW–129M2 7.5 ft 06/23/09 E 0.91

MW–129M2 Pumped 06/23/09 1.4

MW–142M2 Pumped 06/08/09 12

MW–142M2 2.5 ft 06/23/09 9.0

MW–142M2 4.1 ft 06/23/09 11

MW–142M2 5.8 ft 06/23/09 10

MW–142M2 7.5 ft 06/23/09 7.3

MW–142M2 Pumped 06/23/09 9.9

MW–211M1 -6.0 ft 09/02/10 80

MW–211M1 -4.0 ft 09/02/10 77

MW–211M1 -2.0 ft 09/02/10 76

MW–211M1 0.ft 09/02/10 72

Well no. Sample 

designation

Sample 

date 

(mm/dd/yy)

Perchlorate

(μg/L)

MW–211M1 2.5 ft 09/02/10 74

MW–211M1 4.1 ft 09/02/10 71

MW–211M1 5.8 ft 09/02/10 72

MW–211M1 7.5 ft 09/02/10 83

MW–211M1 Pumped 09/02/10 75

MW–368M1 -6.0 ft 09/02/10 60

MW–368M1 -4.0 ft 09/02/10 61

MW–368M1 -2.0 ft 09/02/10 63

MW–368M1 0.ft 09/02/10 64

MW–368M1 2.5 ft 09/02/10 65

MW–368M1 4.1 ft 09/02/10 64

MW–368M1 5.8 ft 09/02/10 62

MW–368M1 7.5 ft 09/02/10 55

MW–368M1 Pumped 09/02/10 63

MW–368M2 -6.0 ft 09/02/10 65

MW–368M2 -4.0 ft 09/02/10 63

MW–368M2 -2.0 ft 09/02/10 61

MW–368M2 0.ft 09/02/10 63

MW–368M2 2.5 ft 09/02/10 64

MW–368M2 4.1 ft 09/02/10 66

MW–368M2 5.8 ft 09/02/10 65

MW–368M2 7.5 ft 09/02/10 70

MW–368M2 Pumped 09/02/10 42
14 Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater

Comparison of Pumped and Grab Sampling 

Methods

The technical staff of the IAGWSP selected the GRAB1L 

grab sampler for field tests in 29 wells in order to provide 

sufficient data from the third phase of the study for a statistical comparison of the no-purge and pumped sampling methods and to determine if the degree of agreement between the 

methods was affected by location in the groundwater-flow 

system or the depth below the water table of the monitoringwell screens. The GRAB1L sampler was selected because 

of the close agreement of concentrations of ordnance-related 

compounds in water samples collected by the GRAB1L and 

pumped sampling methods in the first phase of the project 

and because of the ease of use of the method and commercial 

availability of the device. For this phase of the study, generally 

only a final sample was collected by pumped sampling following retrieval of the GRAB1L sampler. The results of the field 

tests in the 29 wells are given in table 5.

The degree of agreement between concentrations of 

ClO4

- , RDX, and HMX in the GRAB1L and pumped samples 

collected from the 29 monitoring wells is shown in figure 5. 

The concentrations were in close agreement over the range 

of concentrations measured in the samples, as indicated by 

the distribution of the points in close proximity to the lines of 

equal concentrations (fig. 5). The close agreement was also 

observed for minor, less frequently detected explosive compounds such as 3-nitrotoluene, 2-amino-4,6-dinitrotoluene, 

4-amino-2,6-dinitrotoluene, 2,4-dinitrotoluene, and 2,4,6-trinitrotoluene (table 5). There is no evidence of a systematic bias 

in the concentration differences between the methods on the 

basis of type of compound or concentration level. 

MW–129M1

MW–129M2

MW–142M2

MW–211M1

MW–368M1

MW–368M2

EXPLANATION – 10

– 8

– 6

– 4

– 2

0

2

4

6

8

10

12

0 20 40 60 80 100

Concentration of perchlorate, in micrograms per liter

Depth of sampling point above (–) or below top of well screen, in feet

Screened interval

I

I

I

F F F F F

F

Pumped samples

Figure 4. Vertical profiles of perchlorate concentrations in samples collected by low-flow pumped and rigid porous polyethylene 

diffusion sampling methods in and above the 10-foot-long screened intervals of six monitoring wells near the Impact Area on Camp 

Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010. Concentrations include estimated values 

(identified in table 4). I, initial pumped sample; F, final pumped sample.
Sample designation

Sample 

date

 (mm/dd/yy)

Perchlorate

(μg/L)

HMX

(μg/L)

RDX

(μg/L)

3-Nitrotoluene

(μg/L)

2-Amino-4,6-

dinitrotoluene

(μg/L)

4-Amino-2,6-

dinitrotoluene

(μg/L)

Din

MW–31S-GRAB1L 11/18/09 E 0.42 3.6 6.2 <0.40 1.3 0.82 E MW–31S-PUMPED 11/18/09 <1.0 3.3 5.9 <0.40 1.4 0.65 E MW–31S-GRAB1L-G1 09/01/10 <1.0 1.6 2.5 <0.42 0.99 <0.21 MW–31S-GRAB1L-G2 09/01/10 1.6 1.4 2.2 <0.41 0.97 <0.21 MW–31S-GRAB1L-G3 09/01/10 <1.0 1.8 2.2 <0.42 0.96 0.42 E MW–31S-PUMPED 09/01/10 <1.0 2.3 2.8 <0.40 0.99 0.33 E MW–31M-GRAB1L 11/18/09 <1.0 2.1 0.29 <0.40 0.29 0.59 MW–31M-PUMPED 11/18/09 <1.0 2.3 E 0.18 <0.40 0.31 0.35 MW–76S-GRAB1L 11/16/09 1.2 <0.40 0.69 <0.40 <0.20 <0.20 MW–76S-PUMPED 11/16/09 1.5 E 0.14 0.91 <0.40 <0.20 <0.20 MW–76M2-GRAB1L 11/16/09 1.8 8.6 17 <0.40 <0.20 <0.20 MW–76M2-PUMPED 11/16/09 1.4 7.3 12 <0.40 <0.20 0.57 MW–76M2-GRAB2L 09/01/10 1.2 6.2 13 <0.43 E 0.10 <0.22 MW–76M2-PUMPED 09/01/10 1.2 5.7 13 <0.42 <0.21 0.30 MW–89M2-GRAB1L 10/26/09 9.5 0.72 18 <0.40 <0.20 <0.20 MW–89M2-PUMPED 10/27/09 9.6 0.75 17 <0.40 <0.20 <0.20 MW–89M2-GRAB1L-G1 09/01/10 11 0.73 17 <0.42 <0.21 <0.21 MW–89M2-GRAB1L-G2 09/01/10 11 -- -- -- -- -- MW–89M2-GRAB1L-G3 09/01/10 11 0.65 19 <0.41 <0.20 <0.20 MW–89M2-PUMPED 09/01/10 11 0.74 17 <0.45 <0.23 <0.23 MW–129M1-GRAB1L 11/16/09 <1.0 <0.40 <0.20 <0.40 <0.20 <0.20 MW–129M1-PUMPED 11/16/09 <1.0 <0.40 <0.20 <0.40 <0.20 <0.20 MW–129M2-GRAB1L 11/16/09 E 0.98 <0.40 <0.20 <0.40 <0.20 <0.20 MW–129M2-PUMPED 11/16/09 E 0.62 <0.40 <0.20 <0.40 <0.20 <0.20 MW–143M3-GRAB1L 10/06/09 5.5 2.9 <0.20 <0.40 <0.20 <0.20 MW–143M3-PUMPED 10/06/09 5.3 3.0 <0.20 <0.40 <0.20 <0.20 

MW–165M2-GRAB1L 11/16/09 1.2 <0.40 <0.20 <0.40 <0.20 E 0.11 <MW–165M2-PUMPED 11/16/09 1.1 <0.40 <0.20 <0.40 <0.20 <0.20 <

Table 5. Concentrations of perchlorate and explosive compounds in water samples collected from monitoring wells near the Impact Area by using loand 1- and 2-liter polyethylene-film grab samplers, Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010.[Samples analyzed by Test America, Arvada, Colo. Sample designation: Well number in tables 1–2 and suffixes; PUMPED, low-flow pumped; GRAB1L, 1-liter polyethylene-fipolyethylene-film grab; Gx, sequence number of grab sample. Locations shown in figure 1. mm/dd/yy, month/day/year; RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine; HMX, octtetrazocine; <, less than value shown; --, no data; E, estimated value; μg/L, microgram per liter]. 
Table 5. Concentrations of perchlorate, and explosive compounds in water samples collected from monitoring wells near the Impact Area by using and 1- and 2-liter polyethylene-film grab samplers, Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010.—Cont

Sample designation Sample date (mm/dd/yy) Perchlorate (μg/L) HMX (μg/L) RDX (μg/L) 3-Nitrotoluene (μg/L) 2-Amino-4,6- dinitrotoluene (μg/L) 4-Amino-2,6- dinitrotoluene (μg/L) 

Din

MW–207M1-GRAB1L 10/26/09 <1.0 0.52 6.3 <0.40 <0.20 <0.20 MW–207M1-PUMPED 10/27/09 <1.0 0.61 7.6 <0.40 <0.20 <0.20 MW–209M1-GRAB1L 10/26/09 <1.0 0.60 7.8 <0.40 <0.20 <0.20 MW–209M1-PUMPED 10/27/09 <1.0 0.48 7.8 <0.40 <0.20 <0.20 MW–211M1-GRAB1L 11/18/09 100 E 0.26 14 <0.40 <0.20 <0.20 MW–211M1-PUMPED 11/18/09 98 E 0.23 12 <0.40 <0.20 <0.20 MW–279M2-GRAB1L 10/20/09 7.8 <0.40 <0.20 <0.40 <0.20 <0.20 MW–279M2-PUMPED 10/20/09 9.3 <0.40 <0.20 <0.40 E 0.078 <0.20 MW–284M2-GRAB1L 11/03/09 5.9 <0.40 E 0.14 <0.40 <0.20 <0.20 MW–284M2-PUMPED 11/03/09 5.8 <0.40 E 0.14 <0.40 <0.20 <0.20 MW–289M2-GRAB1L 10/05/09 1.6 4.7 2.1 <0.40 <0.20 <0.20 MW–289M2-PUMPED 10/06/09 2.5 4.0 2.4 <0.40 <0.20 <0.20 MW–293M2-GRAB1L 10/05/09 2.3 <0.40 0.22 <0.40 <0.20 <0.20 MW–293M2-PUMPED 10/06/09 2.2 <0.40 0.30 <0.40 <0.20 <0.20 MW–303M2-GRAB1L 10/20/09 2.1 1.9 11 <0.40 <0.20 <0.20 MW–303M2-PUMPED 10/21/09 3.1 2.2 15 <0.40 <0.20 <0.20 MW–303M2-GRAB2L 09/01/10 4.6 4.3 18 <0.41 <0.21 <0.21 MW–303M2-PUMPED 09/01/10 4.0 4.2 17 <0.41 <0.21 <0.21 MW–307M3-GRAB1L 09/22/09 2.3 <0.40 <0.20 <0.40 <0.20 <0.20 MW–307M3-PUMPED 09/22/09 4.4 <0.40 <0.20 <0.40 <0.20 <0.20 MW–313M2-GRAB1L 10/13/09 14 <0.40 <0.20 <0.40 <0.20 <0.20 MW–313M2-PUMPED 10/13/09 14 <0.40 <0.20 <0.40 <0.20 <0.20 MW–323M1-GRAB1L 10/20/09 <1.0 E 0.23 1.6 <0.40 <0.20 <0.20 MW–323M1-PUMPED 10/20/09 <1.0 E 0.13 1.5 <0.40 <0.20 <0.20 MW–323M2-GRAB1L 10/20/09 <1.0 0.69 13 <0.40 <0.20 <0.20 MW–323M2-PUMPED 10/20/09 <1.0 0.68 14 <0.40 <0.20 <0.20 MW–323M2-GRAB1L-G1 09/02/10 <1.0 E 0.28 3.3 <0.41 <0.21 <0.21 MW–323M2-GRAB1L-G2 09/02/10 <1.0 E 0.29 3.1 0.57 <0.21 <0.21 MW–323M2-GRAB1L-G3 09/02/10 <1.0 E 0.30 4.2 <0.47 <0.23 <0.23 MW–323M2-PUMPED 09/02/10 <1.0 E 0.32 3.8 E 0.15 <0.21 <0.21 
Sample designation

Sample 

date

 (mm/dd/yy)

Perchlorate

(μg/L)

HMX

(μg/L)

RDX

(μg/L)

3-Nitrotoluene

(μg/L)

2-Amino-4,6-

dinitrotoluene

(μg/L)

4-Amino-2,6-

dinitrotoluene

(μg/L)

Din

MW–324M2-GRAB1L 10/05/09 <1.0 2.1 0.56 <0.40 <0.20 <0.20 MW–324M2-PUMPED 10/06/09 <1.0 2.2 0.55 <0.40 <0.20 <0.20 MW–335M1-GRAB1L 09/22/09 24 <0.40 0.80 <0.40 <0.20 <0.20 MW–335M1-PUMPED 09/22/09 23 <0.40 0.90 <0.40 <0.20 <0.20 MW–368M1-GRAB1L 09/22/09 46 <0.40 1.6 <0.40 <0.20 <0.20 MW–368M1-PUMPED 09/22/09 47 <0.40 1.4 <0.40 <0.20 <0.20 

MW–368M2-GRAB1L 09/22/09 61 E 0.13 12 <0.40 <0.20 <0.20 MW–368M2-PUMPED 09/22/09 58 E 0.18 12 <0.40 <0.20 <0.20 MW–388M2-GRAB1L 10/05/09 <1.0 <0.40 <0.20 <0.40 <0.20 <0.20 MW–388M2-PUMPED 10/06/09 E 0.50 E 0.16 <0.20 <0.40 <0.20 <0.20 MW–393M1-GRAB1L 10/13/09 E 0.92 <0.40 <0.20 <0.40 <0.20 <0.20 MW–393M1-PUMPED 10/13/09 <1.0 <0.40 <0.20 <0.40 <0.20 <0.20 MW–481M2-GRAB1L 10/26/09 <1.0 0.73 7.6 <0.40 <0.20 <0.20 MW–481M2-PUMPED 10/27/09 <1.0 0.51 4.7 <0.40 <0.20 <0.20 90MW0022-GRAB1L 10/06/09 6.5 4.9 E 0.16 <0.40 <0.20 <0.20 90MW0022-PUMPED 10/06/09 9.6 5.1 0.21 <0.40 <0.20 <0.20 

Table 5. Concentrations of perchlorate, and explosive compounds in water samples collected from monitoring wells near the Impact Area by using and 1- and 2-liter polyethylene-film grab samplers, Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010.—Cont
18 Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater

The sign test (Helsel and Hirsch, 2002) was used to 

determine statistically whether the concentrations in samples 

collected by the GRAB1L method were generally larger or 

smaller than the concentrations in samples collected by the 

low-flow pumped method. The paired data for ClO4

- , RDX, 

and HMX were analyzed separately, and only data pairs in 

which the concentrations were above the detection limit 

(nonzero values) were included in the analysis. The sign tests 

indicate that there is no bias in the concentration differences 

at a Type I risk level of α = 0.01 (number of paired values and 

computed p-values were 20 and 1.000 for ClO4

- , 19 and 0.815 

for RDX, and 21 and 0.824 for HMX, respectively).

To determine if the degree of agreement between the 

methods was affected by the location of the monitoring well 

in the groundwater-flow system, the monitoring wells were 

divided into groups based on water-table altitude. The selected 

ranges in water-table altitudes of 68–71, 56–68, and 5–38 ft 

correspond to locations with gentle, intermediate, and steep 

horizontal hydraulic gradients, respectively (fig. 1). Near the 

top of the water-table mound (water-table altitude of 68–71 ft), 

the horizontal component of groundwater flow generally is 

small, and downward flow may be substantial (Walter and 

Masterson, 2003; Walter and LeBlanc, 2008). In contrast, 

near the coast (water-table altitude of 5–38 ft) the horizontal 

component of groundwater flow generally is large, and upward 

flow also may be substantial. These patterns of flow may affect 

the rate of ambient flow laterally through and vertically within 

the wells screens and, therefore, affect the comparability of the 

samples obtained by the various no-purge sampling methods. 

There is no evidence from the field tests, however, of a systematic bias in concentration differences between the methods 

on the basis of location of the monitoring wells relative to the 

top of the water-table mound (fig. 6).

To determine if the degree of agreement between the 

methods was affected by the depth of the well screens below 

the water table, the monitoring wells were divided into groups 

having shallow (15–53 ft), intermediate (66–105 ft), and deep 

(106–186 ft) screen depths. The aquifer sediments generally become finer grained with depth (Walter and Masterson, 

2003), and groundwater-flow rates therefore may be slower 

with increasing depth. Wells with screens set deep below the 

water table have longer water columns above the screens than 

wells with screens set near the water table. The longer water 

columns could affect natural circulation within the wells and, 

although not likely, the integrity of the no-purge samples 

owing to the long retrieval distances. There is no evidence 

from the field tests, however, for a systematic bias in concentration differences between the methods on the basis of the 

depth of the well screen below the water table (fig. 7).

Figure 5. Comparison of concentrations of perchlorate, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine (HMX) for concentration ranges of A, 0–120 and B, 0–20 micrograms per liter for pumped and grab samples collected 

from 29 monitoring wells near the Impact Area on Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 

2009–2010. Concentrations include estimated values (identified in table 5) and are plotted as zero values where less than the detection 

limit.

RDX

HMX

Perchlorate

EXPLANATION

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Line of equal concentrations

A

0

5

10

15

20

0 5 10 15 20

Line of equal concentrations

B

Grab sample concentration, in micrograms per literGrab sample concentration, in micrograms per liter

Pumped sample concentration, in micrograms per liter Pumped sample concentration, in micrograms per liter
Comparison of Pumped and No-Purge Sampling Methods 19

Figure 6. Comparison of concentrations of three ordnance-related compounds for concentration ranges of A, 0–120 and B, 0–20 

micrograms per liter, for pumped and grab samples collected from wells grouped by location relative to the altitude of the water table 

near the Impact Area on Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010. Concentration data 

are for perchlorate, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) (not identified 

by compound on the graphs). Concentrations include estimated values (identified in table 5) and are plotted as zero values where less 

than the detection limit.

68–71 feet

56–68 feet

5–38 feet

Altitude of water

table at well

EXPLANATION

Pumped sample concentration, in micrograms per liter Pumped sample concentration, in micrograms per liter

0

20

40

60

80

100

120

0 20 40 60 80 100 120

A

0

10

20

0 10 20

Line of equal concentrations

B

Grab sample concentration, in micrograms per liter

Grab sample concentration, in micrograms per liter

Line of equal concentrations

Figure 7. Comparison of concentrations of three ordnance-related compounds for concentration ranges of A, 0–120 and B, 0–20 

micrograms per liter, for pumped and grab samples collected from wells grouped by depth of screened interval below the water table 

near the Impact Area on Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, 2009–2010. Concentrations 

shown are for perchlorate, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) (not 

identified by compound on the graphs). Concentrations include estimated values (identified in table 5) and are plotted as zero values 

where less than the detection limit.

0

20

40

60

80

100

120

0 20 40 60 80 100 120

15–53 feet

66–105 feet

106–186 feet

Line of equal concentrations

A Grab sample concentration, in micrograms per liter

Depth of screen midpoint 

below water table

EXPLANATION

Pumped sample concentration, in micrograms per liter Pumped sample concentration, in micrograms per liter 

Line of equal concentrations

10

20

0

0

10 20

B Grab sample concentration, in micrograms per liter
20 Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater

Collection of Replicate and Large-Volume 

Samples

The no-purge sampling devices used in this study may 

not provide a sufficient volume of water to collect replicate and spiked samples for quality assurance and control 

(QA/QC) purposes. Groundwater-monitoring programs often 

require QA/QC data for legal and regulatory reasons. During the fourth phase of the study, an approach for collection 

of replicate samples that is similar to traditional bailing was 

tested in three wells. A GRAB1L sampler was set in the well, 

left in place for 63–64 days, and then retrieved as described 

above. The sample obtained from this sampler is designated 

GRAB1L-G1 in table 5. A second sampler (GRAB1L-G2) was 

then set in the well and retrieved immediately, followed by a 

third sampler (GRAB1L-G3). A pumped sample was collected 

following retrieval of sample GRAB1L-G3. Although the 

second and third GRAB1L samples were turbid because of 

surging during the sample-collection sequence, the concentrations of ClO4

- , RDX, and HMX in the three GRAB1L samples 

and the corresponding low-flow pumped sample were in close 

agreement for all three wells (table 5).

A second approach for collecting replicate samples with 

a GRAB2L grab sampler was tested in two wells. The volume 

of one GRAB2L sampler (about 2 L) was sufficient to obtain 

as many as three sets of samples for analysis of ClO4

-  and 

explosive compounds, although in this study only one set of 

samples was sent to the laboratory for chemical analysis. The 

concentrations of these compounds in the GRAB2L sample 

and the corresponding low-flow pumped sample were in close 

agreement for both wells (table 5).

Implications of the Choice of Sampling Methods

Concentrations of ClO4

- , RDX, HMX, and other less 

frequently detected explosive compounds in the no-purge and 

low-flow pumped samples were mostly all in close agreement. This field evidence supports the conclusion that diffusion sampling with rigid porous polyethylene (RPPOLY) 

and regenerated-cellulose (RCELLM) membranes, and grab 

sampling with the tubular polyethylene-film samplers, are useful methods for monitoring concentrations of ordnance-related 

compounds at the MMR and in similar hydrogeologic environments. LeBlanc and Vroblesky (2008) reached a similar 

conclusion from their field tests in 15 monitoring wells of the 

RPPOLY samplers. They reported that there was poor agreement between concentrations in RPPOLY and pumped samples in 4 of the 15 wells (MW–31M, MW–76M2, MW165M2, 

and MW–289M2), but they hypothesized that the poor agreement was due to a long time interval between collection of 

the two types of samples and changing concentrations in the 

aquifer during that time. The close agreement between concentrations in GRAB1L and pumped samples in the same wells in 

the present study (table 5) supports their hypothesis. 

The close agreement among concentrations in samples 

collected by all the sampling methods indicates that ambient 

groundwater flow through the monitoring-well screens is sufficiently rapid that the residence time of water in the screens is 

small compared to the 2-week and longer equilibration period 

used in this study. The combination of high hydraulic conductivity in the sand and gravel aquifer and substantial hydraulic 

gradients in most areas contribute to the high flushing rate, 

although direct measurement of these rates was beyond the 

scope of this study. The close agreement may also be due 

to the chemical properties of the explosive compounds and 

ClO4

- , which, unlike VOCs or reactive metals, are not subject 

to loss by volatilization or rapid chemical transformations 

during sample collection. The extrapolation of these results to 

other hydrogeologic settings or to monitoring wells that are 

constructed differently from those tested in this study should 

be done with caution. Archfield and LeBlanc (2005) recommended that a one-time well-by-well comparison between 

pumped and diffusion sample results could determine which 

wells are good candidates for the use of diffusion samplers for 

monitoring concentrations of VOCs at the MMR. A similar 

approach could be used to determine the utility of the no-purge 

sampling method for monitoring explosive compounds and 

ClO4

-  near the Impact Area at the MMR. In a long-term monitoring program that relies on no-purge sampling, confirmation of the no-purge results by comparison to pumped-sample 

results also could be warranted when large or unexpected 

changes in concentrations are observed.

A quantitative comparison of the costs and effort required 

for the various no-purge sampling methods was beyond the 

scope of this study. Several observations may be useful, however, when evaluating which sampling method is best suited to 

a particular monitoring program. One person can implement 

all three methods in the field, although the handling of the four 

RPPOLY samplers is more difficult than the handling of the 

two RCELLM and one GRAB1L sampler. The installation and 

retrieval of the GRAB1L sampler is especially easy because 

the single sampler is suspended at one point at the end of the 

polypropylene line, whereas the RCELLM and RPPOLY samplers are suspended at several points along the weighted line, 

and 2–4 samplers must be processed upon retrieval. An additional advantage of the grab samplers is the option to obtain 

QA/QC samples by using the large-volume GRAB2L sampler 

or multiple grabs with the low-volume GRAB1L sampler.

The three no-purge methods differ most in the effort 

associated with preparation of the sampling devices for installation in the field. The GRAB1L, GRAB2L, and RCELLM 

samplers are used only once and are then discarded, whereas 

the RRPOLY samplers can be cleaned and reused multiple 

times. The GRAB1L and GRAB2L samplers require almost 

no advanced preparation other than attachment of the weights. 

In contrast, the RPPOLY samplers must be filled with deionized water and stored and transported in water so that the 

internal fluid does not drain inadvertently before deployment 

in the wells. The membranes of the RCELLM samplers must 
Summary 21

be rinsed thoroughly before construction of the samplers, and 

the samplers also must be filled and transported in deionized water. The relative importance of these factors should be 

considered when evaluating which device best fits a proposed 

monitoring program.

Summary

A long-term sampling program is an important part of 

most groundwater-remediation efforts. The sampling program typically consists of collection of groundwater samples 

from monitoring wells by using low-flow pumped sampling 

methods and involves considerable cost and effort. No-purge, 

or passive, sampling methods have been developed as a useful 

alternative to pumped sampling. The no-purge methods are 

based on the concept that natural flow through the well screen 

results in the same chemical concentrations in the screen and 

adjacent formation. The no-purge methods include diffusion 

sampling, in which the sampling device consists of a diffusion 

membrane that is filled with a sampling fluid such as deionized water, and grab samplers that consist of a device that is 

lowered into the well screen to capture the groundwater in 

the screen.

Diffusion samplers that are constructed with polyethylene 

diffusion membranes are used at the Massachusetts Military 

Reservation (MMR) to monitor concentrations of volatile 

organic compounds in Cape Cod’s sand and gravel aquifer. 

This study examined the utility of diffusion samplers that 

are constructed of rigid porous polyethylene (RPPOLY) and 

regenerated-cellulose (RCELLM) membranes and two sizes 

(1 L and 2 L) of polyethylene-film grab samplers to monitor 

concentrations of ordnance-related compounds near the Impact 

Area of Camp Edwards at the MMR. The study extends 

the findings from a 2008 investigations report by LeBlanc 

and Vroblesky, which demonstrated that RPPOLY diffusion 

sampling was a useful alternative to pumped sampling for 

monitoring ClO4

- , RDX, HMX, and other minor explosive 

compounds in the contaminant plumes near the Impact Area. 

The study was conducted in a total of 36 monitoring wells 

constructed of 2- or 2.5-in.-diameter PVC casing and approximately 5- to 10-ft-long slotted PVC screens.

In the first phase of the study, RPPOLY and RCELLM 

no-purge samplers and 1-L grab samplers were compared to 

pumped sampling in six wells. At each well, no-purge samplers were set sequentially following the collection of an initial pumped sample, and a final pumped sample was collected 

within 24 hours of retrieval of the last no-purge sampler. In all 

six wells, the concentrations of ClO4

- , RDX, and HMX in the 

no-purge and pumped samples were in close agreement. There 

was no evidence of a systematic bias in concentration differences among the methods on the basis of the type of sampling 

device, the type of contaminant, or the order in which the nopurge samplers were deployed in the well.

The second phase of the study examined whether vertical 

variations in concentrations along the screened interval are 

present that could affect the sampling results, given that the 

sampling methods differ in where and how the samples are 

obtained. Samples were collected for ClO4

-  analysis by using 

4–8 RPPOLY samplers set at 2-ft intervals along and as much 

as 6 ft above the top of the 10-ft-long screens of six wells. 

Small variations in concentrations of ClO4

-  were measured 

in all six wells, but the variations generally were less than 

15 percent of the average concentration for the RPPOLY 

samplers in a given well. In five of the six wells, the average 

concentrations for the RPPOLY samplers also agreed closely 

with the concentrations in the pumped samples. The cause for 

the anomalous result in the sixth well is unknown.

Grab sampling with the 1-L sampler (GRAB1L) was 

compared to pumped sampling in 29 wells during the third 

phase of the study. Concentrations of ClO4

- , RDX, HMX, and 

other less frequently detected explosive compounds in water 

samples collected by grab and pumped sampling were in close 

agreement for all the wells. A sign test was used to determine 

if there was a statistically significant bias in the concentration 

differences between the methods. There was no evidence of a 

bias at the Type I risk level of α=0.01. There was also no evidence for a systematic bias in concentration differences on the 

basis of the location of the monitoring well relative to the top 

of the water-table mound or the depth of the well screen below 

the water table. Groundwater-flow rates that affect the ambient 

flow through the well screen, which in turn could affect the 

utility of no-purge sampling methods, are likely to be related 

to these two factors.

In the final phase of the study, two methods to obtain 

the larger sample volumes that may be needed for quality 

assurance and control (QA/QC) samples were field-tested in 

five wells. The tests demonstrated that sample collection by 

using a larger volume 2-L grab sampler and sequential bailing 

with a smaller volume 1-L grab sampler were possible options 

for obtaining sufficient volumes for replicate and spiked 

QA/QC samples.

The evidence from the field tests supports the conclusion 

that diffusion sampling with RPPOLY and RCELLM membranes and grab sampling with the two sizes of polyethylenefilm grab samplers (1 L and 2 L) are methods for monitoring 

concentrations of ordnance-related compounds at the MMR 

and in similar hydrogeologic environments that provide comparable data to that obtained by low-flow pumped sampling. 

The high groundwater-flow velocities and the chemical properties of the explosive compounds and ClO4

- , which are not 

subject to loss by volatilization or rapid chemical transformations during sample collection, are factors favoring the utility 

of the no-purge sampling methods at the MMR. The applicability of no-purge sampling for monitoring concentrations of 

ordnance-related compounds in other hydrogeologic settings 

or different monitoring-well designs should be confirmed by 

site-specific comparisons similar to those conducted in this 

study.
22 Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater

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Prepared by the Pembroke Publishing Service Center.

For more information concerning this report, contact:

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U.S. Geological Survey

Massachusetts-Rhode Island Water Science Center

10 Bearfoot Road

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dc_ma@usgs.gov

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Savoie and LeBlanc—Comparison of Sampling Methods for Monitoring Concentrations of Ordnance-Related Compounds in Groundwater—Scientific Investigations Report 2012–5084