U.S. Department of the Interior

U.S. Geological Survey

Guidance on the Use of PassiveVapor-Diffusion Samplers to Detect 

Volatile Organic Compounds in 

Ground-Water-Discharge Areas, and 

Example Applications in New England

By PETER E. CHURCH, DON A. VROBLESKY, and FOREST P. LYFORD, 

U.S. Geological Survey, and RICHARD E. WILLEY, 

U.S. Environmental Protection Agency

Water-Resources Investigations Report 02-4186

In cooperation with the

U.S. ENVIRONMENTAL PROTECTION AGENCY

Monitoring and Measurement for the 21st Century Initiative

Northborough, Massachusetts

2002
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information write to: Copies of this report can be purchased from:

Chief, Massachusetts-Rhode Island District U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

10 Bearfoot Road Box 25286

Northborough, MA 01532 Denver, CO 80225-0286

or visit our Web site at

http://ma.water.usgs.gov
Contents III

CONTENTS

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

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

Advantages and Limitations of Passive-Vapor-Diffusion Samplers...................................................................................... 3

Advantages .................................................................................................................................................................. 3

Limitations .................................................................................................................................................................. 4

PART 1. Guidance on the Use of Passive-Vapor-Diffusion Samplers .................................................................................. 5

By Don A. Vroblesky

Assembly of Samplers ................................................................................................................................................ 5

Deployment of Samplers ............................................................................................................................................ 9

Recovery of Samplers ................................................................................................................................................. 13

Factors Affecting Deployment of Samplers and Data Interpretation.......................................................................... 16

Quality Control and Assurance ................................................................................................................................... 17

PART 2. Example Applications in New England.................................................................................................................. 18

Eastern Surplus Company Superfund Site, Meddybemps, Maine .............................................................................. 20

By Forest P. Lyford and Edward M. Hathaway

Description of Study Area................................................................................................................................. 20

Purpose and Design of Sampling ...................................................................................................................... 23

Results ............................................................................................................................................................... 23

McKin Company Superfund Site, Gray, Maine .......................................................................................................... 25

By Forest P. Lyford, Terrence R. Connelly, and Laura E. Flight

Description of Study Area................................................................................................................................. 25

Purpose and Design of Sampling ...................................................................................................................... 25

Results ............................................................................................................................................................... 28

Nutmeg Valley Road Superfund Site, Wolcott and Waterbury, Connecticut .............................................................. 28

By John R. Mullaney, Peter E. Church, and Carolyn J. Pina-Springer

Description of Study Area................................................................................................................................. 28

Purpose and Design of Sampling ...................................................................................................................... 31

Results ............................................................................................................................................................... 31

Baird & McGuire Superfund Site, Holbrook, Massachusetts..................................................................................... 34

By Jennifer G. Savoie and Melissa G. Taylor

Description of Study Area................................................................................................................................. 34

Purpose and Design of Sampling ...................................................................................................................... 34

Results ............................................................................................................................................................... 34

Allen Harbor Landfill, Davisville Naval Construction Battalion Center Superfund Site, North 

Kingstown, Rhode Island .............................................................................................................................. 37

By Forest P. Lyford, William C. Brandon, and Christine A. P. Williams

Description of Study Area................................................................................................................................. 37

Purpose and Design of Sampling ...................................................................................................................... 37

Results ............................................................................................................................................................... 40

Calf Pasture Point, Davisville Naval Construction Battalion Center Superfund Site, North Kingstown, 

Rhode Island.................................................................................................................................................. 40

By Forest P. Lyford, Christine A. P. Williams, and William C. Brandon

Description of Study Area................................................................................................................................. 40

Purpose and Design of Sampling ...................................................................................................................... 43

Results ............................................................................................................................................................... 43

Otis Air National Guard/Camp Edwards Superfund Site, Johns Pond, Falmouth, Massachusetts............................. 43

By Jennifer G. Savoie and Denis R. LeBlanc

Description of Study Area................................................................................................................................. 43
IV Contents

Purpose and Design of Sampling ...................................................................................................................... 45

Results ............................................................................................................................................................... 45

Nyanza Chemical Waste Dump Superfund Site, Ashland, Massachusetts ................................................................. 48

By Forest P. Lyford, Richard E. Willey, and Sharon M. Hayes

Description of Study Area................................................................................................................................. 48

Purpose and Design of Sampling ...................................................................................................................... 51

Results ............................................................................................................................................................... 51

Centredale Manor Restoration Project Superfund Site, North Providence, Rhode Island.......................................... 52

By Peter E. Church, Forest P. Lyford, and Anna F. Krasko

Description of Study Area................................................................................................................................. 52

Purpose and Design of Sampling ...................................................................................................................... 54

Results ............................................................................................................................................................... 54

Quality-Assurance Procedures .................................................................................................................................... 54

Summary and Conclusions.................................................................................................................................................... 56

References Cited ................................................................................................................................................................... 58

Appendix 1. Laboratory and Field Testing of Passive-Vapor-Diffusion Sampler Equilibration Times, Temperature 

Effects, and Sample Stability .................................................................................................................................. 63

By Don A. Vroblesky

Equilibration Times and Temperature Effects ............................................................................................................ 65

Sample Stability .......................................................................................................................................................... 71

Appendix 2. Field Screening of Volatile Organic Compounds Collected with Passive-Vapor-Diffusion Samplers 

with a Gas Chromatograph...................................................................................................................................... 73

By Scott Clifford

FIGURES

1–9. Photographs showing:

1. Glass vial in two layers of polyethylene tubing ............................................................................................ 2

2. Passive-vapor-diffusion samplers with (A) vial and screw cap, (B) uncapped glass vial sealed in 

polyethylene tubing and secured to wire surveyor flag, and (C) glass vial sealed in polyethylene 

sandwich bags and secured to wire surveyor flag ......................................................................................... 6

3. Heat sealing of glass vial in polyethylene tubing.......................................................................................... 7

4. Glass vial positioned in sandwich bag so that a single layer of low-density polyethylene is tight 

across the opening and the self-locking nylon tie does not interfere with capping....................................... 8

5. Installation method for passive-vapor-diffusion samplers in water 0 to 2 feet deep..................................... 10

6. Drive-point assembly for installation of passive-vapor-diffusion sampler in water 2 to 4 feet deep 

in clayey silt to coarse sand and gravel sediments........................................................................................ 11

7. Drive-point method for installation of passive-vapor-diffusion sampler in water 2 to 4 feet deep 

in clayey silt to coarse sand and gravel sediments........................................................................................ 12

8. Screwing a septated cap onto a glass vial encased in the inner low-density polyethylene tubing ................ 14

9. (A) Attaching and (B) crimping a septated cap onto a glass vial encased in the inner low-density 

polyethylene tubing ....................................................................................................................................... 15

10–21 Maps showing:

10. Locations of sites in New England where passive-vapor-diffusion samplers have been used to 

detect and delineate discharge areas of ground water contaminated by volatile organic compounds 

into surface-water bodies............................................................................................................................... 19

11. Location of the Eastern Surplus Superfund Site and study area, Meddybemps, Maine ............................... 21

12. Potentiometric surfaces and generalized ground-water-flow directions for the surficial and 

bedrock aquifers, Eastern Surplus Superfund Site, Meddybemps, Maine, April 30, 1997........................... 22

13. Concentrations of tetrachloroethene (PCE) in passive-vapor-diffusion samplers installed 

in river-bottom sediments on the western edge of Dennys River, Meddybemps, Maine,

October 1996 ................................................................................................................................................. 24

14. Location of the McKin Superfund Site and study area, potentiometric surface contours for 

the surficial aquifer, and extent of trichloroethene in ground water, Gray, Maine........................................ 26
Contents V

15. Locations of passive-vapor-diffusion samplers installed in river-bottom sediment along and 

near the Royal River in September and October 1997, and extent of trichloroethene in ground 

water, Gray, Maine ........................................................................................................................................ 27

16. Concentrations of trichloroethene in passive-vapor-diffusion samplers installed in river-bottom 

sediments near Boiling Springs, Gray, Maine, September and October 1997 .............................................. 29

17. Location of the Nutmeg Valley Road Superfund Site and study area, Nutmeg Valley, Wolcott 

and Waterbury, Connecticut .......................................................................................................................... 30

18. Concentrations of trichloroethene plus tetrachloroethene in passive-vapor-diffusion samplers 

installed in river-bottom sediments of the Mad River, Old Tannery Brook, and an unnamed stream, 

Nutmeg Valley, Wolcott and Waterbury, Connecticut, July 1997 ................................................................. 32

19. Concentrations of trichloroethene plus tetrachloroethene in passive-vapor-diffusion samplers 

installed in river-bottom sediments of the Mad River, Old Tannery Brook, and an unnamed stream, 

Nutmeg Valley, Wolcott and Waterbury, Connecticut, November 1997 ....................................................... 33

20. Location of the Baird & McGuire Superfund Site and study area, Holbrook, Massachusetts...................... 35

21. Concentrations of trichloroethene plus tetrachloroethene and petroleum compounds in 

passive-vapor-diffusion samplers installed in river-bottom sediments of the Cochato River, 

Baird & McGuire Superfund Site, Holbrook, Massachusetts, March and April 1998 ................................. 36

22. Aerial photograph showing locations of the Allen Harbor Landfill and Calf Pasture Point study areas, 

Davisville Naval Construction Battalion Center Superfund Site, North Kingstown, Rhode Island...................... 38

23–33. Maps showing:

23. Directions of ground-water flow in the shallow and deep surficial aquifers, concentrations

of volatile organic compounds in ground water beneath the Allen Harbor Landfill, December 1995,

and concentration of trichloroethene in passive-vapor-diffusion samplers installed in tidal-zone 

sediments along the shoreline of Allen Harbor Landfill, April 1998, Davisville Naval Construction 

Battalion Center Superfund Site, North Kingstown, Rhode Island............................................................... 39

24. Potentiometric surfaces and generalized ground-water-flow directions for the shallow and deep 

surficial aquifers, Calf Pasture Point, Davisville Naval Construction Battalion Center Superfund 

Site, North Kingstown, Rhode Island, December 1995 ................................................................................ 41

25. Concentrations of trichloroethene in passive-vapor-diffusion samplers installed in the tidal-zone 

sediments along the shoreline and in wetland-bottom sediments near the shoreline, Calf Pasture 

Point, Davisville Naval Construction Battalion Center Superfund Site, North Kingstown, Rhode 

Island, March and April 1998 ....................................................................................................................... 42

26. Locations of the Johns Pond study area and Storm Drain-5 contaminant plume, and the altitude of 

water table (March 1993), Cape Cod, Massachusetts ................................................................................... 44

27. Concentrations of trichloroethene plus tetrachloroethene in passive-vapor-diffusion samplers 

installed in pond-bottom sediments adjacent to the Storm Drain-5 contaminant plume, Johns Pond, 

Cape Cod, Massachusetts, August 1998 ....................................................................................................... 46

28. Concentrations of trichloroethene in passive-vapor-diffusion samplers installed in pond-bottom 

sediments in the zones where high concentrations (greater than 10,000 part per billion by volume) 

of trichloroethene were detected with passive-vapor-diffusion samplers in August 1998, Johns Pond, 

Cape Cod, Massachusetts, December 1998 .................................................................................................. 47

29. Discharge areas delineated with passive-vapor-diffusion samplers, August and December 1998, 

and ground-water pathways of the Storm Drain-5 plume and trichloroethene plumes, Johns Pond, 

Cape Cod, Massachusetts.............................................................................................................................. 48

30. Location of Nyanza Chemical Waste Dump Superfund Site, passive-vapor-diffusion sampler 

locations, potentiometric-surface contours for the surficial aquifer, and directions of ground-water 

flow, Ashland, Massachusetts ....................................................................................................................... 49

31. The extent of contaminants in ground water and concentrations of chlorobenzene and 

trichloroethene detected in passive-vapor-diffusion samples, Nyanza Chemical Waste Dump 

Superfund Site, Ashland, Massachusetts, February 1999 ............................................................................. 50

32. Locations of the Centredale Manor Restoration Project Superfund Site and study area, North 

Providence, Rhode Island.............................................................................................................................. 52
VI Contents

33. Concentrations of trichloroethene plus tetrachloroethene in passive-vapor-diffusion samplers 

installed in channel-bottom sediments of the Woonasquatucket River, a former mill raceway, and 

a cross channel, Centredale Manor Restoration Project Superfund Site, North Providence, Rhode 

Island, September 1999 ................................................................................................................................. 53

1A–1D. Graphs showing:

1A. Changes in concentrations of volatile organic compounds in passive-vapor-diffusion samples over 

time at 21 degrees Celsius under laboratory conditions in a mixed solution of volatile organic 

compounds with aqueous concentrations less than 100 micrograms per liter .............................................. 68

1B. Changes in concentrations of volatile organic compounds in passive-vapor-diffusion samples over 

time at 10 degrees Celsius under laboratory conditions in a mixed solution of volatile organic 

compounds with aqueous concentrations ranging from 430 to 570 micrograms per liter ............................ 69

1C. Ratio over time of (A) toluene and (B) tetrachloroethene gas concentrations by volume (parts 

per billion) in passive-vapor-diffusion samplers to aqueous concentrations by mass (210 to 

310 micrograms per liter of toluene and 110 to 340 micrograms per liter of tetrachloroethene) 

in a test solution containing the diffusion samplers in 1.9-liter jars at average temperatures of 

22.4, 9.5, and 1.4 degrees Celsius ................................................................................................................. 70

1D. Changes in trichloroethene concentrations over time in passive-vapor-diffusion samples from 

contaminated ground-water discharge areas in South Carolina in (Site 1) Coastal Plain sediments 

and (Site 2) Piedmont sediments with differing sediment types and vertical hydraulic gradients................ 71

TABLES

1. Volatile organic compounds detected under field conditions with passive-vapor-diffusion samplers 

at contaminated ground-water-discharge areas in New England and South Carolina and the range of 

minimum reporting limits for these compounds at the nine New England sites .................................................... 3

2. Superfund sites in New England where passive-vapor-diffusion samplers were used to detect and 

delineate volatile organic compounds in bottom sediment of surface-water bodies, hydrologic setting, 

principal compounds detected, and maximum vapor concentration measured ...................................................... 20

3. Number and distribution of duplicate samples from the nine study sites in New England .................................... 55

4. Relative percent differences of volatile organic compound (VOC) concentrations in duplicate samples 

where a VOC was detected above the reporting limit in both samples from the nine study sites in 

New England........................................................................................................................................................... 56

1A. Average concentrations and standard deviations of volatile organic compounds in passive-vapor-diffusion 

samplers over time at 21 degrees Celsius under laboratory conditions in 480-milliliter test jars with 

spiked concentrations less than100 micrograms per liter ....................................................................................... 66

1B. Average concentrations and standard deviation of volatile organic compounds in passive-vapor-diffusion 

samplers over time at 10 degrees Celsius under laboratory conditions in 1.9-liter test jars with spiked 

concentrations ranging from 430 to 570 micrograms per liter ............................................................................... 66

1C. Ratio of concentrations from passive-vapor-diffusion samplers to aqueous-phase concentrations for 

toluene and tetrachloroethene over time at various temperatures under laboratory conditions in 1.9-liter 

test jars containing 210 to 310 micrograms per liter of toluene and 110 to 340 micrograms per liter of 

tetrachloroethene..................................................................................................................................................... 67

1D. Average concentrations and standard deviations of trichloroethene over time in passive-vapor-diffusion 

samples in bottom sediment of streams at contaminated ground-water discharge areas in the Coastal Plain 

(site 1) and the Piedmont (site 2) of South Carolina, 1998..................................................................................... 72

2A. Typical achievable reporting limits for volatile organic compounds commonly detected in passive-vapordiffusion samplers from a gas chromatograph equipped with a photoionization detector and an electron

capture detector....................................................................................................................................................... 76

2B. Vapor concentrations of volatile organic compounds commonly detected with passive-vapor-diffusion 

samplers in the head space of a 10 micrograms per liter aqueous standard at approximately

0 to 1 degree Celsius............................................................................................................................................... 77

2C. Quality controls, acceptance criteria, and corrective actions.................................................................................. 79
Contents VII

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS

CONVERSION FACTORS

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

°F = 1.8°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. 

ABBREVIATIONS

μg/L micrograms per liter

mg/L milligrams per liter

mL milliliter

mol/m3 moles per cubic meter

PCE tetrachloroethene

ppb v parts per billion by volume

PVC polyvinylchloride

PVD sampler passive-vapor-diffusion sampler

SVOCs semi-volatile organic compounds

TCE trichloroethene

VOCs volatile organic compounds

cis-DCE cis-1,2-dichloroethene

Concentration of chemical constituents in air are given in parts per billion by volume (ppb v).

Concentration of chemical constituents in water are given in micrograms per liter (μg/L).

Multiply By To obtain

acre 0.4047 hectare

feet (ft) 0.3048 meters

feet per day (ft/d) 0.3048 meters per day

inches (in.) 2.54 centimeters

mil 0.0254 millimeters

square feet (ft2) 0.0929 square meters

Introduction 1

Guidance on the Use of PassiveVapor-Diffusion Samplers to Detect 

Volatile Organic Compounds in 

Ground-Water-Discharge Areas, and 

Example Applications in New England

By Peter E. Church, Don A. Vroblesky, Forest P. Lyford, and Richard E. Willey

Abstract

Polyethylene-membrane passive-vapordiffusion samplers, or PVD samplers, have been 

shown to be an effective and economical reconnaissance tool for detecting and identifying volatile organic compounds (VOCs) in bottom 

sediments of surface-water bodies in areas of 

ground-water discharge. The PVD samplers consist of an empty glass vial enclosed in two layers 

of polyethylene membrane tubing. When samplers 

are placed in contaminated sediments, the air in 

the vial equilibrates with VOCs in pore water. 

Analysis of the vapor indicates the presence or 

absence of VOCs and the likely magnitude of 

concentrations in pore water. 

Examples of applications at nine hazardouswaste sites in New England demonstrate the utility 

of PVD samplers in a variety of hydrologic settings, including rivers, streams, ponds, wetlands, 

and coastal shorelines. Results of PVD sampling 

at these sites have confirmed the presence and 

refined the extent of VOC-contaminated groundwater-discharge areas where contaminated ground 

water is known, and identified areas of VOCcontaminated ground-water discharge where 

ground-water contamination was previously 

unknown. The principal VOCs detected were 

chlorinated and petroleum hydrocarbons. Vapor 

concentrations in samplers range from not 

detected to more than 1,000,000 parts per billion 

by volume. These results provided insights about 

contaminant distributions and ground-water-flow 

patterns in discharge areas, and have guided the 

design of focused characterization activities. 

INTRODUCTION

Passive-vapor-diffusion (PVD) samplers are 

designed and primarily used as a reconnaissance 

tool to detect and identify volatile organic compound 

(VOC) contaminated ground water discharging into 

surface-waters bodies at and near hazardous-waste 

sites (Vroblesky and others, 1996; Vroblesky and 

Robertson, 1996; Vroblesky and Hyde, 1997). Determining the location of discharging contaminated 

ground water is important for plume mapping, evaluating risk potential to human health and the environment, 

and designing focused site-characterization and monitoring activities. Applications of PVD samplers at and 

near nine hazardous-waste sites in New England demonstrated the samplers’ effectiveness in detecting and 

delineating VOCs in a variety of hydrologic settings 

including rivers, streams, ponds, wetlands, and coastal 

shorelines. The PVD samplers also have been used successfully as passive-soil-gas samplers in unsaturated 

zones to map ground-water contamination (Vroblesky 

and others, 1992). 
2 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

The PVD samplers, developed by the U.S. 

Geological Survey (USGS) (Vroblesky and others, 

1996) consist of an empty, uncapped, glass vial 

enclosed in two layers of low-density polyethylene 

membrane tubing (fig. 1) that are permeable to many 

VOCs of environmental interest, such as petroleum and 

chlorinated compounds (table 1), but not permeable to 

water (Vroblesky and others, 1991). When samplers 

are buried in VOC-contaminated pore water in the 

bottom sediment of surface-water bodies, an equilibrium begins to develop between VOC concentrations in 

water and the air in the vial. Equilibrium times, which 

are dependent on many factors such as hydraulic conductivity of the sediment and temperature of the pore 

water, generally range from 1 to 3 weeks. During sampler recovery the outer tubing, which is used to prevent 

sediment, which may be contaminated, from coming 

into contact with the inner tubing and the opened 

vial, is removed. A cap is then screwed on to the vial, 

thereby securing the inner tubing tight against the vial 

opening to prevent loss of VOCs vapor in equilibrium 

with water concentrations at the sampler deployment 

point.

Concentrations of VOCs detected in air in a sampler indicate vapor-phase concentrations in sedimentpore water. The relative concentration partitioning into 

the air and water varies among VOCs and is described 

by Henrys’ law constant for the particular VOC. A 

compound with a relatively high vapor pressure and 

low solubility will tend to become more concentrated 

in the vapor phase than in the water phase. Several of 

VOCs with lower vapor pressure tend to be more concentrated in the water phase, but still maintain a vaporphase signature. Because the low-density polyethlene 

membrane tubing is not a major barrier to VOC diffusion over time, PVD samplers provide a vapor phase 

into which VOCs can diffuse from the aqueous phase. 

The VOCs in water near PVD samplers diffuse through 

the tubing into the air within the glass vial. Vaporphase concentrations in the vial are typically reported 

in parts per billion by volume (ppb v).

In theory, these vapor concentrations can be converted to concentrations in water through Henry’s Law 

and Henry’s Law constants for specific chemicals. In 

practice, however, uncertainties about Henry’s Law 

constants, pore-water temperatures, equilibration times 

for various types of sediments, and analytical precision, 

limit this application. If concentrations in water are 

needed, however, a modification of this approach, 

which is a single layer, water-filled membrane tubing 

sampler, will provide aqueous-phase VOC concentrations in a ground-water-discharge area (Vroblesky and 

others, 1999). 

The ease of constructing, deploying, and retrieving PVD samplers renders this method well-suited for 

reconnaissance of VOC plumes discharging to surface 

waters. A large amount of spatial data can be collected 

in a short period with PVD samplers. For example,

Figure 1. Glass vial in two layers of polyethylene tubing.
Advantages and Limitations of Passive-Vapor-Diffusion Samplers 3

from experience with PVD samplers in New England, 

construction of samplers, deployment of samplers in 

streambed sediments at 50 ft intervals along a 2,000 ft 

reach, retrieval of samplers after equilibration is 

reached (about two weeks), and on-site chemical 

analysis, may be accomplished in a total of three days. 

Results from this sampling may guide the placement of 

well points in shallow waters and monitoring wells or 

the selection of sediment-sampling locations where 

VOCs in water and sediments are detected. Once vapor 

concentrations of VOCs are detected with the PVD 

samplers, then water samples can be collected with 

other methods.

This report describes advantages and limitations 

of PVD samplers, offers guidance on the use of PVD 

samplers, and summarizes results from nine sites in 

New England where PVD samplers have provided 

useful information about VOC plumes in ground water. 

The report is designed mainly for personnel who are 

designing characterization studies that may include 

the use of PVD samplers and for personnel who will 

be constructing and installing the samplers. This 

report was prepared by the U.S. Geological Survey in 

cooperation with the U.S. Environmental Protection 

Agency (USEPA) Technical Innovation Office (TIO), 

and USEPA’s Region I.

The authors acknowledge the following individuals, who are members of agencies within the Federal 

Remediation Technologies Roundtable (FRTR), for 

reviews of this report: Kathryn Davies, Vincent Malott, 

Katherine Baylor, Jeffrey Johnson, Richard Muza, 

and Ernest Waterman, USEPA, Ground Water Forum; 

Deborah Sherer and Kristie Dymond, USEPA, Office 

of Solid Waste and Emergency Response; Dominic C. 

DiGiulio and Timothy Canfield, USEPA, National 

Risk Management Research Laboratory, Ada, OK; 

Charles Porfert, USEPA, New England Office of 

Environmental Measurements and Evaluation; Robert 

Lien, USEPA, National Risk Management Research 

Laboratory, Cincinnati, OH; Chung-Rei Mao, Stephen 

White, and Jeffrey L. Breckenridge, U.S. Army Corps 

of Engineers, Center of Expertise; and Doug Zillmer, 

U.S. Naval Facilities Engineering Command Service 

Center. In addition, we also acknowledge George H. 

Nicholas, New Jersey Department of Environmental 

Protection on behalf of the Interstate Technology and 

Regulatory Cooperation (ITRC), Diffusion Sampler 

Team, for his review of this report.

ADVANTAGES AND 

LIMITATIONS OF PASSIVEVAPOR-DIFFUSION SAMPLERS

Advantages and limitations are presented here, 

before the details of PVD-sampler assembly, deployment, and recovery are described, to ensure that project 

design personnel who may be considering or are planning to use PVD samplers understand capabilities of 

this method. These advantages and limitations may 

also be useful for technicians who assemble, deploy, 

and recover these samplers.

Advantages

1. The PVD method takes advantage of converging 

ground-water-flow lines and upward hydraulic 

gradients at ground-water-discharge areas to 

bring the target contaminants into contact with 

the samplers.

2. The method has been effective in delineating 

VOC-contamination-discharge areas beneath 

surface-water bodies.

3. PVD samplers can be areally and vertically 

distributed to gain information on contaminantdischarge heterogeneity. 

Table 1. Volatile organic compounds detected under field 

conditions with passive-vapor-diffusion samplers at 

contaminated ground-water-discharge areas in New England 

and South Carolina and the range of minimum reporting 

limits for these compounds at the nine New England sites

Volatile organic compound

Range of minimum

reporting limits,

in parts per billion

by volume 

Benzene .................................... 6 to 25

Ethylbenzene ............................ 40 to 90

meta/para-xylene...................... 40 to 90

ortho-xylene ............................. 60 to 100

Toluene ..................................... 20 to 40

Tetrachloroethene ..................... 5 to 25

Trichloroethene......................... 5 to 25

Chlorobenzene.......................... 40 to 70

cis-1,2-Dichloroethene ............. 25 (a target compound at only 

one site)

1,1,1-Trichloroethane ............... 8 (a target compound at only 

one site)

methyl tert butyl ether .............. Not a target compound at the 

New England sites 
4 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

4. The samplers are inexpensive. A low-cost sampler 

can be made from grocery-store sandwich bags 

and empty glass vials. 

5. In many situations, the samplers are easy to 

deploy and recover.

6. Sampler recovery is rapid. The data can be analyzed on site with field gas chromatography, 

or the capped samples can be stored for later 

analysis. A stability test with 40-mL volatile 

organic analysis (VOA) vials showed that VOC 

concentrations in unpunctured, sealed vials did 

not substantially decrease in over 121 hours 

(Vroblesky and others, 1996).

7. Because the pore size of low density polyethylene 

tubing is about 10 angstroms or less, sediment 

does not pass through the membrane into the 

bag. The outer bag, therefore, effectively prevents contaminated soil from contacting the 

inner bag. 

8. A variation of a PVD sampler can be used as a 

soil-gas sampler in unsaturated sediment to 

delineate shallow VOC plumes (Vroblesky and 

others, 1992). Vapor-filled polyethylene 

samplers also can be used with a sorbent to 

allow the samplers to accumulate VOC concentrations over the deployment period (Vroblesky 

and others, 1991). Still another variation consists of water-filled, low-density polyethylene 

tubing sampler deployed in bottom sediments 

at ground-water-discharge areas to yield aqueous concentrations of VOCs (Vroblesky and 

others, 1999).

Limitations

1. Because the change in VOC concentrations within 

PVD samplers in response to changes in ambient concentrations typically takes 24 hours or 

longer, VOC concentrations within the samplers represent an integration of concentrations 

from the most recent part of the deployment 

period until the samplers attain equilibrium. 

The equilibration time depends on several factors, including the temperature and the rate of 

water movement past the sampler. Under laboratory conditions, equilibration times in static 

water ranged from about 24 hours at 21°C to 

about 102 hours at 10°C. Under field conditions, equilibration times can range from as 

little as 12 hours in a rapidly discharging 

unconsolidated sand, to three weeks or more in 

colder, less permeable sediment. Suggested 

PVD deployment periods are typically two 

weeks, but may vary depending on site-specific 

temperature and hydraulic conditions. The 

required equilibration time is a disadvantage 

over some types of real-time sampling methods, such as extracting water from a core or 

pumping water from a small-diameter probe. 

Unlike these methods, however, the PVD samplers can provide an undisturbed sample, which 

minimizes the risk of short-term concentration 

changes from sediment disturbance and reduces 

the uncertainty associated with the source of 

water from a sample obtained from pumping.

2. The PVD samplers are appropriate only for 

volatile compounds.

3. Analysis of the samples requires a gas 

chromatograph.

4. Deployment of the samplers in shallow waters 

typically is a simple task; however, deployment 

in deep waters may require the services of 

SCUBA divers or other installation methods.

5. In some streams, the source of detected VOCs 

may not be readily determined without further 

work because of complexities in hydraulics and 

sediment heterogeneity that lead to unusual 

contaminant-discharge distributions. For example, in some streams of the Rocky Mountains 

region, where ground-water-flow direction is 

approximately parallel to streamflow, locations 

of ground-water-discharge areas can change 

with time. Furthermore, if the samplers are 

deployed in an area of VOC-contaminated 

bottom sediment derived from sediment transport along the stream, then the VOC concentrations in the PVD samplers may reflect 

contaminant concentrations in the sediment 

rather than in discharging ground water. Consequently, an effort should be made to ensure that 

the sampling location is a gaining reach.

6. The samplers must be deployed in an area where 

ground water is discharging to surface water to 

adequately reflect ground-water concentrations. 

In areas where the water in contact with the 

PVD samplers is largely infiltrated surface 

water, the concentrations detected by the PVD 
Assembly of Samplers 5

samplers probably will represent surface-water 

or sediment-contaminant concentrations rather 

than ground-water concentrations. 

7. Transient flow of ground water, such as bank 

storage after a flood wave or tidal cycle, may 

cause temporary or cyclic changes in concentrations of VOCs that could affect interpretations about the extent and concentration level of 

VOCs in ground water.

8. Follow-up studies that use other sampling methods are needed to determine actual concentrations of VOCs in water, if that is a goal of the 

study. The PVD samplers provide VOC concentrations as a gas. Because the partition 

between aqueous and vapor phases depends on 

several factors, such as temperature and pressure, which may vary from site to site and are 

not always known, calculations of aqueousphase concentrations from PVD samplers 

should be considered estimates. An alternative 

approach to obtaining aqueous-phase VOC 

concentrations in a ground-water-discharge 

area is to use a water-filled, low-density polyethyene sampler as described elsewhere (Vroblesky and others, 1999).

9. Caution should be used when deploying PVD 

samplers in streambeds subject to rapid erosion, 

because the samplers may be washed away. 

Samplers also may be difficult to find when the 

surveyor flags are submerged in high flows in 

streams or buried beneath sediment as flows 

recede. 

PART 1. GUIDANCE ON THE 

USE OF PASSIVE-VAPORDIFFUSION SAMPLERS

By Don A. Vroblesky

This section of the report provides guidance on 

PVD-sampler assembly, deployment, and recovery to 

detect volatile organic compounds in ground-waterdischarge areas. As an aid to ensure proper use of this 

method and interpretation of the data collected, factors 

affecting PVD-sampler deployment, data interpretation, and quality control and assurance, are also 

discussed.

ASSEMBLY OF SAMPLERS

Several approaches may be used to construct a 

PVD sampler. A vial may be enclosed in "lay-flat," 

low-density polyethylene (LDPE) tubing, flexible 

tubing that is laid flat and wound-up in a roll, and then 

heat-sealed at both ends, or the vial may be enclosed in 

zipper-type sealable sandwich bags (fig. 2). The vials 

should be glass and sealable with a septated cap. Typical vials used include 20-mL crimp-top glass vials and 

40-ml volatile organic analysis (VOA) glass screw-top 

vials. Vials used in the studies summarized in this 

report are 40-mL VOA screw-top vials. When the 

20-mL crimp-top glass vials are used, 2-, 3-, or 4-mil 

LDPE may be used for the bag material. When 40-mL 

VOA vials are used, 2- or 3-mil LDPE for the inner 

material is advised, because the cap is difficult to screw 

onto 4-mil LDPE. The septum for the cap should be 

Teflon or Teflon coated. The effort for constructing 

PVD samplers is approximately equivalent for the two 

methods. Also, the material costs differ little between 

methods, except for the initial purchase of a heat sealer 

if constructing samplers with tubing. The LDPE tubing, however, is more resilient to punctures and abrasion during placement and retrieval, and is therefore 

preferred to construction with sandwich bags, particularly for placement in coarse gravels.

To construct a PVD sampler from lay-flat LDPE 

tubing and a heat sealer, the following supplies are 

needed: 2-in. wide (approximately 1.5-in. diameter), 

2-, 3-, or 4-mil lay-flat LDPE tubing; a glass vial, a 

wire surveyor flag, self-locking nylon ties, and a heat 

sealer. The following approach describes a typical 

PVD-construction sequence.

1. Cut an 8-in. length of 2-in. wide lay-flat LDPE 

tubing. The inner layer of tubing should be 2- 

or 3-mil thick when VOA vials are used and 2-, 

3-, or 4-mil when crimp-top serum vials are 

used. For the studies summarized in this report, 

40-mL VOA screw-top vials were used.

2. Heat-seal one end. The heat sealer should be 

adjusted to provide a uniform seal without 

melting through the LDPE. Multiple seals may 

be required with some heat sealers with less 

than 400 watts of impulse power.

3. Insert an uncapped empty 40-mL glass VOA vial 

or a 20-mL crimp-top serum vial into the tube. 

Store the cap in a clean environment away 

from the PVD samplers until the sample is 

recovered.
6 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

4. Remove the excess air space from the LDPE tubing. This can be accomplished by squeezing the 

LDPE tubing tightly against the vial or by 

twisting the tubing to tighten it against the vial.

5a. Position the unsealed end of the bag across the 

sealing element of the heat sealer, so that the 

sealing element is as close as practical to the 

mouth of the enclosed vial without stretching 

the LDPE across the opening (fig. 3). The 

LDPE should not be folded or wrinkled where 

it crosses the heating element of the heat sealer. 

Seal the bag. Once the bag is sealed, trim off 

the excess LDPE tubing. In this method, the 

LDPE is not necessarily tight across the vial 

opening.

5b. An optional method to arranging the heat-sealed 

end of the inner LDPE tubing across the vial 

opening is to, after both ends of the tubing are 

sealed, pull the tubing over the vial opening and 

fold the heat-sealed end of the tubing against 

the glass vial. After folding, secure the folded 

tubing to the vial with a self-locking nylon tie 

in a place where it will not interfere with 

attaching a vial cap during sampler recovery. In 

this method, the LDPE should be tight against 

the vial opening. This method improves sampler integrity over the first method because it 

reduces the probability of accidentally cutting 

the inner LDPE while removing the outer 

LDPE during sampler recovery.

Figure 2. Passive-vapor-diffusion samplers with (A) vial and screw cap, (B) uncapped glass vial sealed in polyethylene 

tubing and secured to wire surveyor flag, and (C) glass vial sealed in polyethylene sandwich bags and secured to wire 

surveyor flag.

A. B. C.
Assembly of Samplers 7

6. Once the inner LDPE tubing is secure, cut another 

8-in. length of 2-in. wide lay-flat LDPE tubing. 

This tubing will constitute the outer layer, 

which will be removed during sampler recovery 

to prevent sediment from interfering with 

capping the vials.

7. Heat-seal one end. The heat sealer should be 

adjusted to provide a uniform seal without 

melting through the LDPE. Multiple seals may 

be required with some heat sealers with less 

than 400 watts of impulse power.

8. Place the glass vial enclosed in the inner layer of 

LDPE into the new LDPE tube. 

9. Press the LDPE against the vial to remove the 

excess air space from the outer LDPE tubing. 

The lack of air space will reduce buoyancy and 

maintain a consistent vapor volume. 

10. Position the unsealed end of the bag across the 

sealing element of the heat sealer so that the 

sealing element is as close as practical to the 

mouth of the enclosed vial. No folds or wrinkles should be present where the LDPE tubing 

crosses the heating element of the heat sealer. 

Seal the bag. Once the bag is sealed, trim off 

the excess LDPE tubing.

11. Attach a wire surveyor flag to the PVD sampler to 

aid in sampler recovery. A practical method of 

attachment is to use self-locking nylon ties. The 

ties are attached tightly enough so that the surveyor flag does not pull free from the sampler 

during sampler recovery. The vial is attached so 

that the vial opening is in the opposite direction 

of the surveyor flag (fig. 2). One approach is to 

allow approximately 2 in. of wire extending 

beyond the nylon tie. The 2 in. of wire is then 

bent back 180 degrees over the nylon tie and 

laid adjacent to the wire above the tie. Add 

another nylon tie to secure the bent part of the 

wire tight against the vial (fig. 2). By this 

method, the surveyor flag does not pull free 

from the sampler during retrieval. The widest 

practical spacing between nylon ties will 

reduce a tendency for samplers to rotate on 

the wire and become wedged in sediment 

during retrieval.

The following method details how to construct a 

sampler with sandwich bags instead of lay-flat tubing.

1. Place an uncapped empty glass vial in a zippertype polyethylene sandwich bag. Store the cap 

in a clean environment away from the PVD 

samplers until sampler recovery.

Figure 3. Heat sealing of glass vial in polyethylene tubing.
8 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

2. Remove the excess air space from the bag to 

reduce buoyancy of the sampler when 

deployed. This can be accomplished by squeezing or rolling the bag around the vial. Seal the 

bag with the zipper. 

3. Secure the bag around the vial opening by tightening a self-locking nylon tie below the vial 

opening so that the tie and the excess bag will 

not interfere with capping the vial. A single 

layer of LDPE should now be tight across the 

vial opening (fig. 4). 

4. Place the glass vial enclosed in the LDPE bag into 

another sandwich bag. Remove excess air from 

the outer bag and seal it with the zipper. 

5. Attach a wire surveyor flag to the PVD sampler to 

aid in sampler recovery. A practical method of 

attachment is to use self-locking nylon ties. The 

ties are attached tightly enough so that the surveyor flag does not pull free from the sampler 

during sampler recovery. The vial is attached so 

that the vial opening is in the opposite direction 

of the surveyor flag (fig. 2). One approach is to 

allow approximately 2 in. of wire extending 

beyond the nylon tie. The 2 in. of wire is then 

bent back 180 degrees over the nylon tie and 

laid adjacent to the wire above the tie. Add 

another nylon tie to secure the bent part of the 

wire tight against the vial (fig. 2). By this 

method, the surveyor flag does not pull free 

from the sampler during retrieval. The widest 

practical spacing between nylon ties will 

reduce a tendency for samplers to rotate on the 

wire and become wedged in sediment during 

retrieval.

Figure 4. Glass vial positioned in sandwich bag so that a single layer of low-density 

polyethylene is tight across the opening and the self-locking nylon tie does not interfere with 

capping.
Deployment of Samplers 9

DEPLOYMENT OF SAMPLERS

Effective use of the samplers to delineate discharging contaminated ground water requires that samplers be deployed in ground-water-discharge areas. 

Many approaches have been used to identify gaining 

reaches of streams (zones where ground water discharges to surface water). To verify that the target section of the surface water is a gaining reach, install a 

streambed piezometer. In its simplest form, a streambed piezometer can be a pipe driven a few feet into the 

bed sediment. A bolt loosely fitted into the bottom of 

the pipe before installation can prevent sediment from 

moving into the pipe. After deployment a narrow rod 

then can be used to drive out the bolt to allow water to 

enter the pipe. After stabilization, comparison of 

ground-water-head measurements within the piezometer to surface-water stage outside the piezometer can 

indicate whether the head gradient is upward (gaining 

reach) or downward (losing reach). With this method, 

care should be taken to avoid a clogged pipe or a pipe 

with a leaky connection to surface water along the 

annular space between pipe and streambed sediments.

Many other methods have been used to identify 

areas of upwelling ground water beneath surface water. 

Near-shore discharge through a lakebed has been estimated with seepage devices (Lee, 1977) and hydraulic 

potentiomanometers (Winter and others, 1988). In 

areas where temperature differences between ground 

water and surface water are greater than normally 

expected, surface-water-temperature measurements 

and aerial infrared photography have been used to 

identify areas of ground-water discharge to streams 

(Silliman and Booth, 1993), lakes, and wetlands 

(Olafsson, 1979; Lee, 1985; Lee and Tracey, 1984; 

Baskin, 1998). Discharge areas of ground water to 

lakes sometimes can be located by towing temperature 

and specific-conductance probes from a boat (Lee, 

1985). Researchers also have used the distribution of 

aquatic plant species as indicators of ground-water 

discharge to fens (Glaser and others, 1981; 1990; 

Verhoeven and others, 1988; Wassen and others, 1989), 

to saline wetlands (Swanson and others, 1984), and to a 

lake (Rosenberry and others, 2000). 

Even within gaining reaches of a stream, 

the distribution of contaminant discharge can be 

complex. After storms, ground-water discharge may 

be dominated by release of bank storage. This 

transient flow may temporarily mask contaminated 

ground-water discharge.

Deployment of PVD samplers involves burying 

of samplers in the bottom sediment of a surface-water 

body. Ideally, the samplers should be buried at the 

bottom of the transition zone from surface water to 

ground water to ensure that the sample collected represents VOCs in ground water. Delineating the transition 

zone, however, often is difficult, and holes dug beneath 

the water tend to rapidly refill with sediment. Samplers 

placed at shallow depths (for example, 0 to 0.5 ft) may 

be within this transition zone and samples may be 

affected by surface water. Samplers placed at shallow 

depths may also become dislodged. Samplers placed 

at greater depths (for example, greater than 1.5 ft) may 

be below the transition zone, but also may be difficult 

to retrieve. The most effective depths of sampler 

deployment may vary spatially and with time, and are 

dependent on many factors, including hydraulic conductivities of the sediments and hydrologic conditions. 

With the deployment method described, a practical 

target depth is between 0.5 and 1.5 ft. Deployment 

depths are described in detail more in the section 

"Factors Affecting Deployment of Samplers and Data 

Interpretation."

In shallow waters, waters up to 2 ft deep, where 

the samplers can be installed with hand augers or shovels (fig. 5), one approach to digging the hole is to 

shovel the sediment until the likelihood of hole collapse makes further digging impractical. At that point, 

insert the shovel into the sediment and push forward 

to create an opening between the back of the shovel 

and the sediment. In more cohesive sediment, the hole 

can be excavated with a hand auger. Exercise care 

during insertion of the PVD sampler into the hole to 

prevent rupturing of the polyethylene membrane covering the vial opening. Backfill the hole with the inserted 

PVD sampler with the sediment removed from the 

hole. Ensure that the hole has been adequately backfilled above the sampler to minimize entrainment of the 

top-most sediment layer above the PVD sampler to the 

bottom of the hole. To reduce the potential for contamination from sample-labeling pens, label the surveyor 

flag either several days before PVD-sampler construction (to allow vapors from water-proof markers to 

dissipate) or after the sampler is buried.
10 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England Figure 5. Installation method for passive-vapor-diffusion samplers in water 0 to 2 feet deep. (A) passive-vapor-diffusion sampler secured to wire surveyor flag and tools used for installation, (B) insertion of sampler in space behind flattened surface of steel bar driven into cobble bottom sediments, and (C) passive-vapor-diffusion sampler installed.36" A. B. C.
Deployment of Samplers 11

In water deeper than about 2 ft, manual 

insertion of a sampler in a hand-augered hole or 

behind a shovel blade is not practical in conventional wading gear (hip or chest waders). A 

drive-point assembly has been effective in water 

2 to 4 ft deep where chest waders are needed. 

The drive-point assembly has also been used 

from a row boat (Campbell and others, 2002) 

and through an ice cover (Lyford and others, 

2000; Church and others, 2002) to install samplers in soft bottom sediment at depths to about 

7 ft. Greater depths of installation may be possible from a boat, barge, or through ice, but has 

not been attempted. The drive-point assembly 

and its application are illustrated in figures 6 

and 7.

Drive-point assemblies can be constructed at various lengths to suit different 

needs. The drive-point assembly most commonly used in New England studies consists of 

a 72-in. long, 1 3/4-in. outside diameter (OD), 

1 5/8-in. inside diameter (ID) electrical conduit 

outer pipe; a 74-in. long, 1 1/2-in. OD, 1 3/8-in. 

ID electrical conduit inner pipe; and an 80-in. 

long, 7/8-in. OD, 3/4-in. ID polyvinylchloride 

(PVC) pipe. A 2-in. OD pipe cap is attached to 

the top of the 1 1/2-in. inner pipe, and a 2-in. 

long steel point is flush-mounted to the bottom. 

The outer and inner pipes are driven into the 

bottom sediments by striking the pipe cap on 

the inner pipe with a sledge or slide hammer. At 

the desired depth of installation, the inner pipe 

is removed, leaving a hole in the sediment 

extending about 2-in. deeper than the bottom of 

the outer pipe. The surveyor flag end of the 

PVD sampler is then pushed into the PVC pipe 

to where it is stopped by the tubing of the sampler. The PVC pipe and attached sampler are 

then inserted and pushed through the outer 

pipe into the sediment. The sampler is held in 

place by the PVC pipe as the outer pipe is 

removed. Sediments then collapse around the 

sampler, and the PVC pipe is removed from the 

sediment. 

Figure 6. Drive-point assembly for installation of passive-vapordiffusion sampler in water 2 to 4 feet deep in clayey silt to coarse sand 

and gravel sediments. (A) slide hammer, (B) 1 5/8-inch inside diameter 

steel electrical conduit, (C) 1 3/8-inch inside diameter steel electrical 

conduit with machined point, (D) polyvinylchloride sampler-insertion 

pipe.

80"

A.

B. C.

D.
12 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 7. Drive-point method for installation of passive-vapor-diffusion sampler in water 2 to 4 feet deep in clayey silt to coarse 

sand and gravel sediments. (A) 1 5/8-inch inside diameter (ID) steel electrical conduit with 1 3/8-inch ID steel insert conduit with 

2-inch point driven into pond-bottom sediment with slide hammer, (B) insert pipe removed after driven to desired depth, (C)

insertion of passive- vapor-diffusion sampler to polyvinylchloride (PVC) pipe (surveyor flag and wire inserted into pipe with 

sampler exposed), (D) insertion of PVC pipe with sampler into sediment through 1 5/8-inch ID steel conduit, (E) removal of 1 5/8-

inch ID steel conduit, and (F) removal of PVC pipe leaving sampler installed in sediment.

A. B. C.

D. E. F.
Recovery of Samplers 13

At depths greater than 4 ft, divers may be needed 

to install PVD samplers. Divers have been used to 

install samplers in pond-bottom sediment to pond 

depths of 30 ft (Savoie and others, 2000). Divers 

inserted PVD samplers in soft sediment by hand and 

used a trowel in gravelly sediments.

For studies in New England, the samplers were 

found to be resistant to removal by high flows if 

buried to depths of 8 in. or greater into the sediment. 

Less than five percent of the approximate 1,250 samplers installed in the New England sites were lost. In 

a few instances, firmly planted samplers were not 

found when the surveyor wire flag broke free from 

the self-locking nylon ties upon retrieval, or when 

stream-channel sediment buried the flag.

RECOVERY OF SAMPLERS

The amount of time PVD samplers must remain 

deployed in the sediment before recovery is, in part, 

based on the data-quality objective of the study. If the 

objective is to identify the presence or absence of 

VOC(s), samplers could be recovered within a few 

days. Field studies suggest that this can be accomplished after a deployment period of 8 days or less, 

and as little as 24 hours in some environments. If the 

objective is to estimate the concentration(s) of VOC(s), 

samplers cannot be recovered until enough time for 

equilibrium has elapsed. As discussed earlier, several 

factors, such as hydraulic conductivity of streambed 

sediments, hydraulic gradients, and water temperatures, affect the amount of equilibration time needed. 

Field evidence, discussed in Appendix I, suggests that 

an equilibrium period of approximately 2 weeks is adequate for most investigations in sandy formations. 

Longer or shorter periods may be appropriate depending on water temperatures and hydraulic conditions. It 

is important to remember, however, that PVD samplers 

typically are deployed in sediments as a reconnaissance 

tool to locate areas where ground water contaminated 

with VOCs is discharging. For this use, determining the 

presence or absence of target VOCs may be sufficient 

to meet the data-quality objectives of the sampling. A 

recent study showed that within 24 hours in four separate streams, the recovered PVD samplers contained 

chlorinated aliphatic compounds from discharging 

ground water at concentrations well above detection 

limits, although the samplers had not yet equilibrated 

with the ground water concentrations at three of the 

sites (Vroblesky and Campbell, 2001). 

Recovery of PVD samplers can be accomplished 

relatively rapidly. A 2-member team is needed; one 

person with “dirty hands” who retrieves samplers and 

touches the outer tubing only; the other person with 

“clean hands” who caps and stores samplers and 

touches the inner tubing only. A second clean hands 

person may be needed in situations where sets of samplers (10 or 20 samplers) are delivered to an on-site 

portable laboratory several times a day, and to assist in 

labeling and note taking. The specific recovery steps 

are listed below: 

1. Pull the surveyor flag or excavate the sediment to 

remove the PVD sampler. Pull with a steady 

tension rather than a sudden forceful extraction 

that can cause nylon ties to break. Examine the 

sampler for integrity. Record unusual features, 

such as discoloring or water inside the outer 

bag. Discard or quickly cap and record a 

sampler with a ruptured inner seal.

2. Cut and remove the outer tubing or bag from 

around the vial opening. Do not pierce or cut 

the inner tubing or bag, because this can allow 

trapped vapors within the vial to escape or 

allow ambient air to enter, resulting in incorrectly low VOC concentrations within the vial. 

An alternative approach to removing the outer 

tubing that reduces the chance of puncturing 

the inner bag is to cut the outer nylon ties. After 

cutting the ties, use scissors to cut the end of 

the outer tubing adjacent the vial opening, and 

then push on the opposite end of the outer 

tubing to slide the sampler into the hands of the 

clean-hands person. Diagonal cutters (electrician’s pliers) are effective for cutting nylon ties 

that attach samplers to surveyor flags. Inspect 

the sampler and record any unusual features, 

such as discoloring or water inside the the inner 

bag. Discard or quickly cap and record a 

sampler with a ruptured inner seal. 

3. Cap the vial by screwing (fig. 8) or crimping 

(fig. 9) a cap onto the vial to seal the inner 

tubing or bag over the vial opening. Use caps 

that have a Teflon or Teflon-lined septum to 

allow sampling by syringe. 
14 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

4. Label the vial after capping if the vial is removed from the labeled surveyor 

flag. The inner tubing or bag may be cut around the bottom of the cap and 

removed to facilitate labeling.

5. Store the PVD samplers away from any potential VOC-contaminant sources 

and in a chilled environment (4°C; ice or refrigerator), to reduce VOC 

leakage. If the vapor in the sampler is to be analyzed immediately, chilled 

storage is not needed.

The vapor sample obtained from the recovered PVD sampler can be analyzed on site with a gas chromatograph. Guidance on the use of a gas 

chromatograph is described in Appendix 2.

Figure 8. Screwing a septated cap onto a glass vial encased in the inner low-density 

polyethylene tubing.
Recovery of Samplers 15

Figure 9. (A) Attaching and (B) crimping a septated cap onto a glass vial encased in the 

inner low-density polyethylene tubing.
16 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

FACTORS AFFECTING 

DEPLOYMENT OF SAMPLERS AND 

DATA INTERPRETATION

The effectiveness of PVD samplers as a reconnaissance tool to detect discharge areas of VOCcontaminated ground water depends on a variety of factors affecting contaminated ground-water discharge. 

Understanding these factors will help in selecting optimal sampler-deployment locations and will aid in data 

interpretation. 

Aquifer and streambed lithologic heterogeneity 

affects discharge complexity and the optimal samplerdeployment locations. Using PVD samplers, Lyford 

and others (1999a) found that an irregular pattern of 

trichloroethene discharge to the Royal River, Maine, 

was related to the lithologic heterogeneity of the aquifer and riverbed sediments, and that significantly 

higher concentrations of contaminants discharged at 

sand boils. Conant (2000) found that contaminant discharge to a river in Ontario was predominantly associated with local gaps in the semi-confining unit beneath 

the river. Discharge of ground water beneath lakebeds 

can be particularly difficult to investigate because the 

water can discharge at low rates over a large area, and 

both rate and area can change with time. Winter (1976, 

1978) has shown that the discharge is controlled predominantly by the spatial distribution of heads and 

hydraulic conductivity in the aquifer, as well as the 

bathymetry and sediment type of the lake bottom. 

Another factor affecting contaminant discharge 

to rivers is the orientation of the river relative to the 

flow direction of the ground-water contamination. An 

investigation in Greenville, South Carolina, showed 

that reaches of a stream that were at a sharp angle to the 

axis of contamination-plume migration received 

greater contaminant discharge than reaches oriented 

approximately parallel to the direction of contaminant 

transport (Vroblesky, 2000). In a channel meandering 

through a tidally flooded wetland, the highest concentrations of discharging contaminants were found where 

the meander approached the shoreline that contained 

the ground-water contamination (Vroblesky and Lorah, 

1991). This area was the most probable contaminantdischarge area because of its proximity to the groundwater contamination, and because the stream reach was 

oriented approximately perpendicular to the groundwater-flow path. Particular effort, therefore, should 

be exercised during sampler deployment in sediment 

beneath a meandering stream to ensure adequate 

density of sampling locations in reaches where the 

stream is oriented at sharp angles to the contaminant 

transport direction. Similarly, care should be exercised 

in wetlands to adequately target zones where channel 

meanders approach the shoreline that contains the 

ground-water contamination.

When deploying samplers in lakes or large 

streams, consideration should be given to the depth of 

the contaminant plume as it approaches the surfacewater body. Knowing this depth will help estimate the 

probable distance of contaminant discharge from the 

shoreline. In thick aquifers, there is often a deeper 

flow system beneath shallow stream subsystems (Toth, 

1963). Thus, contaminant discharge from a distant 

source, which travels in the deep aquifer system, will 

discharge into the surface-water body at a greater distance from the shoreline than nearby contaminants that 

travel in a shallower flow system. Savoie and others 

(2000) found that contaminants emanating from a 

source approximately 1.5 miles upgradient from the 

shoreline of a kettle pond discharged into the pond 

100 to 350 ft offshore. A second previously unknown 

plume was detected discharging into the pond at a 

distance of 25 to 200 ft offshore (Savoie and others, 

2000). Samplers deployed near the shore would not 

have detected these plumes. 

Similar considerations for placement of PVD 

samplers should be given to deployment in streams. In 

an ideal gaining stream with homogeneous bottom sediment and similar ground-water hydraulic gradients 

on both sides of the channel, ground water moving 

beneath a particular shoreline typically discharges to 

the stream closer to that shoreline than to the opposite 

shoreline. In this case, VOCs detected near a particular 

shoreline probably came from ground water derived in 

the upgradient direction of that shoreline. The lithologic and hydrologic complexities of streams, however, 

can create complex discharge pathways, sometimes 

making it difficult to select optimum-sampler 

placement sites and to identify contaminant-source 

directions.

Temporal changes in the locations of discharge 

areas also can affect concentrations of VOCs in discharge and affect interpretation of data from PVD 

samplers. A study of a small Coastal Plain stream in 

South Carolina to which petroleum hydrocarbons were 
Quality Control and Assurance 17

discharging showed that the stream contained an 

upstream gaining reach and a downstream losing reach. 

The boundary between the two reaches migrated 

upstream during periods of low ground-water levels 

and streamflow and downstream during periods of high 

ground-water levels and streamflow (Vroblesky and 

others, 1997). Thus, PVD samplers placed near the 

gaining/losing boundary in this stream can be expected 

to intercept upward moving ground water during part 

of the year and downward moving surface water during 

a different part of the year. Additional temporal variations in contaminant discharge through a streambed 

have been observed following nearby well construction 

(Vroblesky and Robertson, 1996).

Because the VOC concentration within a PVD 

sampler represents an equilibrium between the vapor 

phase in the sampler and the adjacent aqueous solution, 

changing aqueous-contaminant concentrations 

produce a corresponding change in the vapor-phase 

concentrations. If PVD samplers in a local area are 

removed sequentially over time following an equilibration period, they can be used to track temporal changes 

in the contaminant concentrations of discharging 

ground water (Vroblesky and Robertson, 1996). 

Because PVD samplers are sensitive to temporal 

fluctuations, samplers for a particular sampling 

event should all be collected sequentially within a 

few hours of each other to obtain a "snapshot" of the 

contaminant-discharge distribution. 

The depth to which the samplers are installed 

also may affect the results. The samplers should be 

installed at or below the ground-water/surface-water 

interface; however, the location of the interface 

typically is difficult to delineate. It may be at the 

sediment/water interface or at some depth below the 

sediment. In some areas, the interface may shift as a 

result of daily or seasonal fluctuations in river stage 

and ground-water flow. Surface water may enter the 

sediment at the head of riffles and dropoffs and re-enter 

the river at the upstream edge and base of pools (Vaux, 

1968; Boulton, 1993). The surface water also can leave 

the channel laterally and travel through the streambanks before eventually re-entering the channel downstream (Harvey and Bencala, 1993). The movement of 

surface water into bed sediments is more pronounced in 

high permeability sediment than in low permeability 

sediment; therefore, PVD samplers buried in shallow 

sandy horizons in these zones may intercept local 

surface water rather than discharging ground water. 

Contaminated ground water upwelling beneath these 

zones may be diverted and discharge farther downstream (Conant, 2000). For practical reasons, PVD 

samplers often are buried at a uniform depth of approximately 0.5 to 1.5 ft, which may or may not be below 

the ground-water/surface-water interface. It is important, therefore, to consider the implications of subsurface streamflow when interpreting the PVD-sampler 

data.

Furthermore, if the samplers are deployed in an 

area of VOC-contaminated bottom sediment derived 

from sediment transported in the stream, then the VOC 

concentration in the PVD samplers may reflect contaminant concentrations in the sediment rather than in 

discharging ground water. It is important, therefore, to 

consider the possibility of stream transport of contaminated sediment when interpreting PVD data. In some 

cases, this situation probably can be resolved by 

deploying the samplers beneath such sediment.

An additional factor affecting data interpretation 

and sampler deployment is the potential for removal 

of the target compounds by micro-organisms in the 

sediment. The large diversity of micro-organisms and 

oxidation reduction conditions commonly found in 

wetland sediments may lower contaminant concentrations locally. Consequently, PVD samplers buried 

beneath the organic-rich bed sediments may detect a 

substantially higher concentration of VOCs than 

samplers placed in the upper part of the organic-rich 

sediment. In this situation PVD samplers can help 

evaluate VOC loss over a particular interval.

QUALITY CONTROL AND 

ASSURANCE

The primary purpose of most studies that use 

PVD samplers is to determine or verify the presence of 

VOCs. Relative concentrations of VOCs detected at the 

site are also of interest. Variability and bias introduced 

during sample collection, however, affects the interpretation of the results. Confidence in the detections and 

the relative concentrations of VOCs in samples collected with PVD samplers can be evaluated by collecting a series of quality-control (QC) samples, such as 

duplicate, trip, and equipment-blank samples. 
18 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Duplicate or co-located samples provide information needed to estimate the precision of concentration values affected by the combination of uncertainties 

associated with field variability, sample processing, 

and the analytical method. A duplicate PVD sampler 

consists of two separate samplers deployed adjacent to 

each other in the same hole. These samplers are typically held together side-by-side to the same surveyor 

flag with nylon ties to ensure that the open end of the 

vials are at the same depth. To account for sampler 

variability, at least 10 percent of the samplers should be 

duplicates. Examples from studies in New England 

show that a VOC was detected in 1 of the duplicate 

samples but not in the other in only about 2.5 percent of 

the 437 duplicate samples. The relative percent difference (RPD) between VOC concentrations in the 83 

duplicate samples where a VOC was detected in both 

samples ranged from 0 to nearly 200 percent. About 75 

percent of these RPDs, however, were less than 30 percent, which is a reasonable range for a reconnaissance 

tool. Duplicate samplers also can provide a backup in 

case one of the samplers is compromised.

Trip blanks are PVD samplers that are prepared 

offsite, typically with construction of all the samplers 

expected to be used at the site. They are stored and 

transported to the sampling location with the other 

PVD samplers and capped at the sampling location 

when the PVD samplers are deployed. The trip blanks 

are then stored with other samples as they are recovered, and analyzed with the recovered samples. A positive detection in the trip blank means that the PVD 

samplers were exposed to specific contaminant(s) 

sometime before deployment. To some extent, this 

detection imparts a degree of uncertainty to the detections of that specific compound in the recovered PVD 

samples. It should be noted, however, that the samplers 

re-equilibrate to their surroundings. If background 

samples do not contain the specific contaminant, then 

it is highly probable that sufficient deployment time 

elapsed to allow concentrations of the specific contaminant to re-equilibrate to ambient conditions in all of the 

deployed samplers. 

Some of the PVD samplers should be deployed 

in an area of the surface-water body considered to be 

away from potential VOC contamination, such as 

upstream in rivers. If contaminants are found in 

samplers from a target area, but not in the background 

samplers, then this provides increased confidence 

that the contaminants are not an artifact of the 

methodology.

PART 2. EXAMPLE

APPLICATIONS IN 

NEW ENGLAND

During 1996 through 2000, PVD samplers were 

used at nine Superfund sites in New England to identify 

likely discharge areas for VOCs in ground water (fig. 

10). These sites were selected for study because contamination of ground water by VOCs was known or 

suspected. The sites represent a variety of hydrologic 

settings including rivers, streams, ponds, wetlands, and 

coastal shorelines (table 2). Samplers, all constructed 

by methods described in Vroblesky and others (1996), 

were placed in sediments ranging from clayey silt to 

cobbles. Vapor concentrations in samplers ranged from 

not detected to more than 1,000,000 parts per billion by 

volume (ppb v). The principal VOCs detected include 

the chlorinated compounds tetrachloroethene (PCE), 

trichloroethene (TCE), and chlorobenzene, and the 

petroleum compounds benzene, ethylbenzene, metapara-xylene, ortho-xylene, and toluene. At all nine 

Superfund sites, discharge areas of known groundwater plumes contaminated with VOCs were confirmed 

and refined with PVD samplers. At four of these sites, 

results of PVD sampling has lead to the identification 

of previously unknown plumes of contaminated ground 

water and has helped guide further characterization of 

ground water at these sites. The following sections 

briefly describe each of the nine study areas, state the 

purpose and design of PVD sampling, present sampling 

results on maps, and summarize findings. Also 

included is a summary of the quality control and assurance results for the nine studies. These summaries were 

extracted from published reports. Additional detail 

about any of these studies can be found in the cited 

reports.
Quality Control and Assurance 19

Figure 10. Locations of sites in New England where passive-vapor-diffusion samplers have been used 

to detect and delineate discharge areas of ground water contaminated by volatile organic compounds 

into surface-water bodies.
20 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

EASTERN SURPLUS 

COMPANY SUPERFUND SITE,

MEDDYBEMPS, MAINE

By Forest P. Lyford and

Edward M. Hathaway

Description of Study Area

The Eastern Surplus Company in Meddybemps, 

Maine, was a retailer of surplus and salvage items from 

1946 until 1985. Activities at the site caused the release 

of chemicals, including VOCs and polychlorinated 

biphenyls (PCBs), to the environment (E.M. Hathaway, 

U.S. Environmental Protection Agency, written 

commun., 1996). The Eastern Surplus Company 

Superfund site (Eastern Surplus site) covers about 4 

acres adjacent to Meddybemps Lake and the Dennys 

River, which flows from Meddybemps Lake (fig. 11). 

Surficial materials in an approximately 30-acre study 

area that encompasses the site vary widely in texture. 

Materials include till at the northern end and on the 

eastern side of the Dennys River, coarse sand and 

gravel on the western side, silt deposited in a marine 

environment in the central part of the site, and marine 

clay over coarse materials and till on the southern side. 

Surficial materials are generally less than 30 ft thick. In 

some areas, these materials lie above the water table for 

all or much of the time. Ground water in surficial materials under the site generally flows toward the Dennys 

River (fig. 12). Bedrock includes diorite and granite 

where ground water moves in fractures. Ground water 

in bedrock under the site generally flows eastward 

toward Meddybemps Lake at the northern end of the 

site and southward to eastward toward the Dennys 

River elsewhere (fig. 12) (Lyford and others, 1998). 

Some ground water flows toward a depression in the 

bedrock potentiometric surface caused by pumping for 

residential use on the southeastern side of the study 

area.

1May have been derived from adhesive tape used to secure polyethylene membrane to glass vial.

Table 2. Superfund sites in New England where passive-vapor-diffusion samplers were used to detect and delineate volatile 

organic compounds in bottom sediments of surface-water bodies, hydrologic setting, principal compounds detected, and 

maximum vapor concentration measured 

[Concentrations in parts per billion by volume. PCE, tetrachloroethene; TCE, trichloroethene; petroleum compounds, (benzene, toluene, ethylbenzene, 

meta/para-xylene, and ortho-xylene)]

Site Hydrologic setting

Principal

compound(s)

detected

Maximum vapor

concentration

measured

Eastern Surplus Company Superfund Site, Meddybemps, Maine Lake and river PCE

TCE

Toluene1

240

70

2,500

McKin Company Superfund Site, Gray, Maine River TCE 30,400

Nutmeg Valley Road Superfund Site, Wolcott and Waterbury, Connecticut River TCE > 30,000

Baird & McGuire Superfund Site, Holbrook, Massachusetts River Petroleum 

compounds

TCE + PCE

216,000

1,900

Allen Harbor Landfill, Davisville Naval Construction Battalion Center 

Superfund Site, North Kingstown, Rhode Island

Coastal shoreline TCE

PCE

Benzene

340,000

1,700

940

Calf Pasture Point, Davisville Naval Construction Battalion Center 

Superfund Site, North Kingstown, Rhode Island

Coastal shoreline and 

wetland area

TCE (shoreline)

TCE (wetland)

1,900

14

Otis Air National Guard/Camp Edwards Superfund Site, Johns Pond, 

Falmouth, Massachusetts

Pond TCE

PCE

47,000

667

Nyanza Chemical Waste Dump Superfund Site, Ashland, Massachusetts River, former mill 

raceway, and pond

Chlorobenzene

TCE

5,330

1,910

Centredale Manor Restoration Project Superfund Site, North Providence, 

Rhode Island

River and former mill 

raceway

PCE

TCE

1,390,000

182,000
Eastern Surplus Company Superfund Site, Meddybumps, Maine 21

Figure 11. Location of the Eastern Surplus Superfund Site and study area, Meddybemps, Maine.
22 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 12. Potentiometric surfaces and generalized ground-water-flow directions for the surficial and bedrock aquifers, 

Eastern Surplus Superfund Site, Meddybemps, Maine, April 30, 1997.
Eastern Surplus Company Superfund Site, Meddybumps, Maine 23

Purpose and Design of 

Sampling

Sampling of four monitoring wells in 1988 identified one area at the northern end of the site, near well 

MW-3B, where PCE and TCE were present in ground 

water in fractured bedrock (E.M. Hathaway, written 

commun., 1996) (fig. 13). Ground-water sampling 

points were limited, and other areas of ground-water 

contamination were possible. During early phases of a 

study by the USGS in 1996-97, PVD samplers were 

placed along the shore of Meddybemps Lake and the 

west bank of the Dennys River to determine if other 

VOC plumes were present and discharging to surface 

water (Lyford and others, 1998).

To our knowledge, the use of PVD samplers at 

the Eastern Surplus site was the first application in 

New England. Sampler construction included the use 

of adhesive tape to hold the polyethylene membranes 

firmly to bottles. Samplers were placed about 25 to 

50 ft apart along most of the shoreline and river bank 

(fig. 13). Very coarse materials consisting of cobbles 

and boulders along the shoreline and river bank precluded the installation of samplers in some areas. 

During this early attempt to use PVD samplers, the 

most effective method found for installation in the 

coarse materials was by manual insertion in a hole 

formed behind a shovel driven into bottom materials 

and forced forward. The PVD samplers were in place 

for about one month before retrieval and on-site 

analysis of vapors.

Results

The VOCs detected in PVD samplers included 

PCE, TCE, and toluene. The compounds PCE and TCE 

were detected near well MW-3B, where they had been 

detected in ground water (fig. 13). The sample from 

one sampler placed along the Dennys River south of 

the site also contained PCE and TCE. Subsequent 

installation of monitoring wells and ground-water 

sampling in this area identified a previously unknown 

plume of VOCs, mainly PCE, in surficial materials and 

bedrock. The plume appeared to originate at the southern end of the site (Lyford and others, 1998) (fig. 13). 

The extent of this plume, shown on figure 13, is based 

on water samples from wells that were installed after 

the survey with PVD samplers.

Toluene was detected in several PVD samplers 

but not in water from monitoring wells. The toluene 

may have been derived from the adhesive tape used to 

secure the surveyor flag and tubing to the glass vials. 

Similar occurrences of toluene in diffusion samplers 

wrapped with adhesive tape were described by 

Mullaney and others (1999).
24 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 13. Concentrations of tetrachloroethene (PCE) in passive-vapor-diffusion samplers installed in river-bottom 

sediments on the western edge of Dennys River, Meddybemps, Maine, October 1996.
McKin Company Superfund Site, Gray, Maine 25

McKIN COMPANY SUPERFUND 

SITE, GRAY, MAINE

By Forest P. Lyford, Terrence R. 

Connelly, and Laura E. Flight

Description of Study Area

The McKin Company Superfund Site (Mckin 

site) in Gray, Maine, is a former waste-collection, 

transfer, and disposal facility that operated from 1965 

to 1978. Some of the wastes, including petroleum 

hydrocarbons and chlorinated solvents, infiltrated and 

contaminated ground water. A contaminant plume in 

ground water, consisting mainly of TCE, extends 

northward and eastward from the site for several thousand feet (fig. 14). The eastern plume discharges to the 

Royal River in an area known locally as Boiling 

Springs (Sevee and Maher Engineers, Inc., 1999). 

Since at least 1993, concentrations of TCE in most 

monitoring wells have been declining gradually by 

natural attenuation.

 In the Superfund area, TCE in ground water 

is present in surficial materials and fractured crystalline 

rock. The surficial materials consist mainly of 

glacially-derived sand and gravel overlain by a thick 

layer of glaciomarine clay in some areas (Lyford and 

others, 1999a). The marine clays are absent under the 

McKin site, but form a confining layer for ground 

water in buried coarse materials under part of the area 

between the site and the Royal River. In the area near 

Boiling Springs, the Royal River has eroded through 

the marine clays and exposed underlying coarsegrained materials. This area of exposed coarse-grained 

materials is the principal discharge area for the groundwater system to the north and west (fig. 14). Water 

samples from monitoring wells also indicate that the 

discharge of contaminants is focused in the area near 

Boiling Springs (Lyford and others, 1999a). Data from 

the monitoring wells also indicate that the TCE plume 

in fractured granite is coincident with the plume in 

overlying surficial materials. Samples were collected 

with PVD samplers during a period of low flow in the 

Royal River. Historical water-quality data indicate that 

concentrations of TCE in the river near the railroad 

trestle typically range from 15 to 20 μg/L for river 

discharges at the time of the study.

Purpose and Design of 

Sampling

The quantity of TCE that discharges to the Royal 

River, at river flows generally less than 100 ft3/s, is 

great enough to cause concentrations in the river to 

exceed the State of Maine’s water-quality standard 

for streams of 2.7 μg/L (P.R. Jaffe, Princeton 

University, written commun., 1996). In 1996, the 

Maine Department of Environmental Protection 

(MEDEP) and the USEPA sought, from the potentially 

responsible parties (PRPs) for the McKin site, an evaluation of remediation methods to reduce discharge of 

TCE into the river. The PRPs estimated that a 1,500-ft 

long interception system would be needed to successfully capture the TCE plume. Evaluation of remediation strategies and selection of a remediation program 

required an understanding of the configuration of 

the TCE plume near the river and the distribution of 

TCE concentrations across the width of the plume. 

Consequently, PVD samplers were installed along the 

Royal River and an unnamed tributary in the autumn of 

1997 to determine the width of the TCE plume at the 

Royal River and variations in concentrations of TCE 

across the width of the plume (Lyford and others, 

1999a) (fig. 15). In addition to these two goals, it was 

anticipated that results of the study would improve the 

understanding of contaminant pathways near the river.

Approximately 150 PVD samplers were placed 

along the banks of the Royal River and in several 

transects across the width of the river over a 3-day 

period in September 1997. Samplers also were placed 

along an unnamed tributary stream of the Royal River, 

in Boiling Springs, and in a seepage area on the north 

side of the river downstream from a river bend. After 

about 2 weeks, the samplers were retrieved and samples were analyzed on site with a portable gas chromatograph. The PVD samplers were retrieved at about 

the rate that they were analyzed in the field laboratory 

(about 50 per day). No samplers were lost during the 

study.
26 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 14. Location of the McKin Superfund Site and study area, potentiometric surface contours for the surficial aquifer, and 

extent of trichloroethene in ground water, Gray, Maine.
McKin Company Superfund Site, Gray, Maine 27

Figure 15. Locations of passive-vapor-diffusion samplers installed in river-bottom sediment along and near the Royal 

River in September and October 1997, and extent of trichloroethene in ground water, Gray, Maine.

150

150

150

150

100

100

100

150

200

100

14R

EXPLANATION

EXTENT OF TRICHLOROETHENE IN SURFICIAL AQUIFER–Shows 

 the extent of concentrations greater than 2 micrograms per liter. 

 (Data from Sevee and Maher Engineers, Inc., 1998)

PASSIVE-VAPOR-DIFFUSION SAMPLERS

0

0 50 METERS

200 FEET

CONTOUR INTERVAL 10 FEET 

NATIONAL GEODETIC VERTICAL DATUM OF 1929

Base from U.S. Geological Survey digital

line graphs from Gray quadrangle, 1:24,000

Map modified from Lyford and others, 1999a

Maine Central Railroad

Unnamed tributary

Boiling

Springs

Royal River

Area shown in figure 16

railroad

trestle

Flow
28 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Results

The compound TCE was detected in most PVD 

samplers placed downstream of sampler 14R (fig. 16). 

The extent of the plume, as determined with PVD samplers, was generally consistent with plume maps drawn 

on the basis of water samples from wells (Sevee and 

Maher Engineers, Inc., 1998) (fig. 15). The highest 

concentrations, however, were focused in an area 

where sand boils were apparent in the riverbed a few 

hundred feet downstream from Boiling Springs, indicating a major discharge area for ground water and 

contaminants (fig. 16). In this general area, concentrations of TCE also were detected in samplers placed in 

the center of the river and on the opposite side, indicating that contaminated ground water was discharging 

across the width of the river and probably flowing 

beyond the river and floodplain downstream to points 

between the sharp easterly bend in the river and the 

railroad trestle (fig. 16). The VOCs detected downstream of the railroad trestle in an area outside of the 

mapped extent of the plume in ground water may result 

from the exchange of contaminated surface water with 

water in the bottom sediments. Hydraulic head data for 

the sediments and TCE concentrations for the river at 

the time of sampler retrieval would have been useful to 

test this possibility.

NUTMEG VALLEY ROAD 

SUPERFUND SITE, 

WOLCOTT AND WATERBURY,

CONNECTICUT

By John R. Mullaney, Peter E. 

Church, and Carolyn J. Pina-Springer

Description of Study Area

Ground-water contamination by VOCs was 

discovered in the 1980s in the Nutmeg Valley area, 

Wolcott and Waterbury, Connecticut, and the area 

was classified by the USEPA as a Superfund site in 

1989 (U.S. Environmental Protection Agency, 1989) 

(fig. 17), where approximately 43 industries and 25 

residences use ground water, primarily from the bedrock aquifer, for industrial and domestic supply. Past 

disposal of industrial chemicals has been implicated in 

contamination of water from supply wells sampled by 

local, State, and Federal agencies during 1979–95. 

Contaminants may also be contributed to ground water 

from the City of Waterbury landfill (the North End 

Disposal Area), located about 1/2 mi upgradient from 

the Nutmeg Valley Road Superfund Site (fig. 17). The 

VOCs most commonly detected in supply wells tapping the crystalline-bedrock aquifer included TCE, 

PCE, and 1,1,1-trichloroethane (TCA). Concentrations 

of TCE were as high as 320 μg/L in samples collected 

from supply wells in 1985 (Mullaney and others, 

1999).

Two principal aquifers underlie the Nutmeg 

Valley study area—an unconsolidated surficial aquifer 

consisting of glacial till, glacial stratified deposits, and 

postglacial alluvium, and a fractured crystalline bedrock aquifer consisting of well-foliated gneiss and granofels. Glacial till overlies the bedrock and is at land 

surface in most upland parts of the study area. Till is 

generally less than 10 ft thick; locally, however, it is 

more than 25 ft thick. Glacial derived stratified deposits 

in the valley, consisting of poor to well sorted layers of 

gravel, sand, silt and clay, range in thickness from 0 to 

85 ft over till. A semi-confining layer of fine-grained 

deposits within the stratified deposits, 5 to 10 ft thick, 

overlies silty, sand and gravel in an area beneath the 

lower reaches of the unnamed tributary and Old 

Tannery Brook, and short reaches of the Mad River 

upstream and downstream of the confluence with Old 

Tannery Brook. Postglacial alluvial and swamp deposits are generally less than 10 ft thick and overlie glacial 

stratified deposits on the floodplain surfaces of the Mad 

River and Old Tannery Brook. These streams have 

incised deeply into glacial stratified deposits during 

postglacial time. The texture of the alluvium beneath 

the floodplain ranges widely from gravelly sand deposited in former stream-channel positions to fine sand and 

silt with significant amounts of organic material in 

overbank deposits laid down during floods (Mullaney 

and others, 1999).
Nutmeg Valley Road Superfund Site, Wolcott and Waterbury, Connecticut 29

Figure 16. Concentrations of trichloroethene in passive-vapor-diffusion samplers installed in river-bottom 

sediments near Boiling Springs, Gray, Maine, September and October 1997.
30 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 17. Location of the Nutmeg Valley Road Superfund Site and study area, Nutmeg Valley, Wolcott and Waterbury, 

Connecticut.
Nutmeg Valley Road Superfund Site, Wolcott and Waterbury, Connecticut 31

Purpose and Design of Sampling

In 1997, the USGS, in cooperation with the 

Town of Wolcott and the USEPA, used PVD samplers 

as a reconnaissance tool for detecting and delineating 

ground-water discharge of VOCs into the local streams: 

Mad River, Old Tannery Brook, and an unnamed tributary to Old Tannery Brook (Mullaney and others, 

1999). Samplers were installed in the river-bottom 

sediments at 154 sites along the Mad River, Old 

Tannery Brook, and an unnamed tributary of Old 

Tannery Brook on May 12-27, 1997, and were 

retrieved on July 8-10, 1997. Samplers were placed at 

100- to 200-ft intervals in the center of the streams and 

in transects across the stream at selected locations 

(fig. 18). Because the PVD-sampler technology was 

new, a second round of sampling was done for comparison with results obtained from the first round of sampling. On October 23-28, 1997, 128 PVD samplers 

were installed at locations similar to those in the first 

sampling round. These samplers were retrieved on 

November 11-13, 1997 (fig. 19). The USEPA analyzed 

both sets of samples on site with a gas chromatograph 

calibrated for measurement and identification of TCE, 

PCE, and petroleum compounds (Mullaney and others, 

1999). In addition, vertical head gradients between the 

ground water and surface water were measured in 

November 1997 at 30 locations along Old Tannery 

Brook, the unnamed tributary to Old Tannery Brook, 

and the Mad River to determine if and where ground 

water was discharging to the streams.

Results

Results from the first round of sampling show 

that the highest concentrations and most frequent 

detections of VOCs were in zones along the lower 

reach of Old Tannery Brook and in the Mad River at 

short distances upstream and downstream from the 

confluence with Old Tannery Brook (fig. 18). Concentrations of TCE ranged from not detected (less than 

5 ppb v) to 4,800 ppb v. Concentrations of PCE ranged 

from not detected (less than 5 ppb v) to 781 ppb v. 

Adhesive tape used to secure the samplers to the surveyor flags in the first round of sampling was found to 

contain petroleum compounds; therefore, detections of 

these compounds in PVD samples were not reported.

The second round of samplers were retrieved in 

November 1997 to determine if the July 1997 results 

were reproducible. Instead of tape, nylon ties were used 

to secure surveyor flags to the samplers, to avoid problems with contamination by petroleum compounds. 

The spatial pattern of VOCs detected was similar to the 

July 1997 detection pattern (fig. 19), but with fewer 

detections of PCE and with additional locations where 

trace-levels of cis-DCE were detected. This difference 

was due to a small difference in the calibration of the 

gas chromatograph between the two sampling rounds. 

Concentrations of TCE in vapor ranged from not 

detected (less than 25 ppb v) to greater than 30,000 ppb 

v. Concentrations of PCE ranged from not detected 

(less than 25 ppb v) to 390 ppb v. Concentrations of 

benzene ranged from not detected (less than 25 ppb v) 

to 51 ppb v. 

In both sampling rounds, the highest vapor concentrations were detected along the lower reach of Old 

Tannery Brook near a known contaminated area on the 

western side of the brook that contains primarily TCE, 

PCE, vinyl chloride, and cis-DCE in soils and ground 

water (Loureiro Engineering Associates, 1998a, b). 

Ground-water contaminated by TCE also has been documented on the eastern side of Old Tannery Brook 

(HRP Associates, 1991). This area is underlain by the 

fine-grained deposits (semi-confining lacustrine 

deposit), which suggests that VOCs discharged to the 

brook are from contaminated ground water in the postglacial alluvium. The high vapor concentrations of 

TCE detected along the Mad River may be from 

ground-water-contaminant plumes in surficial deposits 

beneath the fine-grained layer, or from the fractured 

bedrock, or both.

In both sampling rounds, vapor concentrations of 

TCE and PCE were detected in the unnamed tributary, 

but were lower than those detected in the Old Tannery 

Brook and the Mad River (figs. 18 and 19). In the first 

sampling round, the highest TCE and PCE vapor concentrations were detected 1,200 ft upstream of the Old 

Tannery Brook; concentration of TCE was 73 ppb v, 

and PCE was 348 ppb v. The highest vapor concentrations in the second sampling round were detected 

1,600 ft upstream of Old Tannery Brook; concentration 

of TCE was 104 ppb v and PCE was 101 ppb v.

Variations in vapor concentrations across stream 

channels were observed at sites where PVD samplers 

were installed at the edges and in the center of the 

channel. These variations are probably due to the direction from which the VOCs originate, and also may 

be caused by variations in organic matter, biotic 

and abiotic processes, and streambed-hydraulic 

conductivity.
32 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 18. Concentrations of trichloroethene plus tetrachloroethene in passive-vapor-diffusion samplers installed in riverbottom sediments of the Mad River, Old Tannery Brook, and an unnamed stream, Nutmeg Valley, Wolcott and Waterbury, 

Connecticut, July 1997.
Nutmeg Valley Road Superfund Site, Wolcott and Waterbury, Connecticut 33

Figure 19. Concentrations of trichloroethene plus tetrachloroethene in passive-vapor-diffusion samplers installed in riverbottom sediments of the Mad River, Old Tannery Brook, and an unnamed stream, Nutmeg Valley, Wolcott and Waterbury, 

Connecticut, November 1997.
34 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

BAIRD & McGUIRE 

SUPERFUND SITE, 

HOLBROOK, MASSACHUSETTS

By Jennifer G. Savoie and 

Melissa G. Taylor

Description of Study Area

A ground-water plume containing volatile and 

semi-volatile organic compounds at the Baird & 

McGuire Superfund Site in Holbrook, Massachusetts, 

extends eastward from a former chemical-processing 

plant toward and beneath the Cochato River (fig. 20) 

(M.G. Taylor, Environmental Protection Agency, 

written commun., 1998). The Cochato River once supplied water to the towns of Holbrook, Randolph, and 

Braintree, but use of this source ended after contamination near the river was discovered in 1983. In 1993, a 

ground-water-extraction system began operation to 

remove contaminants from a sand and gravel aquifer 

below the site and the river and to limit the discharge of 

contaminants to the river. From 1995 to 1997, contaminated sediments were excavated from the river and 

incinerated as part of site remediation. Despite these 

remedial actions, the USEPA and residents are concerned that contaminants from the ground-water plume 

could discharge to the river (Savoie and others, 1999).

Purpose and Design of 

Sampling

In March and April 1998, a network of PVD 

samplers was installed along the Cochato River to 

determine if VOC-contaminated ground water was discharging through the river-bottom sediments while a 

ground-water-extraction system was operating and 

after the system had been shut down for 2 weeks 

(fig. 21). Drive-point piezometers were installed at four 

locations within the riverbed of the Cochato River near 

the known extent of the ground-water plume. Water 

levels from piezometers were compared to river-stage 

measurements to determine if the river was gaining 

ground water across the study area and if contaminants 

could potentially discharge into the river (Savoie and 

others, 1999).

Results

Under pumping and non-pumping conditions, 

petroleum compounds (benzene, ethylbenzene, 

meta/para-xylene, ortho-xylene, and toluene) were 

detected in PVD samplers where the plume passes 

beneath the river (fig. 21, showing concentrations 

under pumping conditions). Concentrations of total 

petroleum compounds ranged from not detected 

upriver of plume area, but downriver adjacent to 

the plume area concentrations were greater than 

200,000 ppb v. Under pumping and non-pumping 

conditions, concentrations did not differ significantly. 

The compounds TCE, PCE, and cis-DCE also were 

detected in PVD samplers more than 200 ft downstream of the area where the petroleum compounds 

were detected. These detections indicate a different 

source for TCE + PCE than for the petroleum 

compounds (fig. 21).

Water levels in four piezometers were consistently higher than the river stage, which indicates an 

upward hydraulic gradient and ground-water discharge 

to the river. This observation in the piezometers and 

the presence of contaminants in the pore water of riverbottom sediments indicate that contaminants from 

the Baird & McGuire Superfund Site ground-water 

plume were discharging into the Cochato River at the 

time of this study for both pumping and non-pumping 

conditions.
Baird & McGuire Superfund Site, Holbrook, Massachusetts 35

Figure 20. Location of the Baird & McGuire Superfund Site and study area, Holbrook, 

Massachusetts.
36 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 21. Concentrations of trichloroethene plus tetrachloroethene and petroleum compounds in passivevapor-diffusion samplers installed in river-bottom sediments of the Cochato River, Baird & McGuire 

Superfund Site, Holbrook, Massachusetts, March and April 1998.
Allen Harbor Landfill, Davisville Naval Construction Battalion Center Superfund Site, North Kingstown, Rhode Island 37

ALLEN HARBOR LANDFILL, 

DAVISVILLE NAVAL CONSTRUCTION 

BATTALION CENTER SUPERFUND 

SITE, NORTH KINGSTOWN, 

RHODE ISLAND

By Forest P. Lyford, William C. 

Brandon, and Christine A.P. Williams

Description of Study Area

The Allen Harbor Landfill at the former 

Davisville Naval Construction Battalion Center in 

North Kingstown, Rhode Island (fig. 22), was used by 

the U.S. Navy from 1946 until 1974 to dispose of 

wastes, including municipal-type waste, construction 

debris, paint thinners, degreasers, sewerage sludge, and 

fuel oil (EA Engineering, Science, and Technology, 

1996). This approximately 15-acre landfill on the 

west side of Allen Harbor is bordered on the west by 

Sanford Road and a large wetland, and is bordered 

on the north and south by small vegetated wetlands 

(fig. 23).

Landfill wastes are up to 20 ft thick. Geologic 

materials beneath landfill wastes and the shoreline 

include a discontinuous layer of fine to very fine sand, 

generally less than 15 ft thick, over a layer of silt that is 

20 to 50 ft thick. Peat layers are in some locations at the 

top of the sand layer. The silt layer overlies a discontinuous till layer or bedrock. The altitude of the bottom of 

the silt layer ranges from 30 to 50 ft below sea level 

(EA Engineering, Science, and Technology, 1996). 

Monitoring wells, some in clusters, are completed in 

the upper sand layer (S following the well number indicates a shallow screen depth), the silt layer (I following 

the well number indicates a intermediate screen depth), 

and till (D following the well number indicates a deep 

screen depth) (fig. 23).

Shallow ground water in landfill wastes and the 

upper sand layer flows eastward from a water-table 

mound centered near well MW09-18I (fig. 23) to the 

shore and southward toward a mudflat area. During the 

wet season, shallow ground water also flows westward 

toward a wetland on the west side of Sanford Road. 

The mound is not apparent in water levels from wells 

screened at greater depths near and below the bottom of 

the silt layer. Ground-water flow at depth is predominantly eastward and southeastward toward Allen 

Harbor (fig. 23). Vertical hydraulic gradients are downward in the area of the water-table mound and upward 

near the shore. Gradients reverse in some wells near 

the shore during high tide, but this reversal has not 

been consistently observed for all tidal cycles (EA 

Engineering, Science, and Technology, 1996).

A variety of VOCs, including petroleum and 

chlorinated compounds have been detected in samples 

from several monitoring wells within the landfill area 

(fig. 23) (EA Engineering, Science, and Technology, 

1996). Concentrations of VOCs also have been 

detected in water from borings installed in sediments 

offshore in the harbor (EA Engineering, Science, and 

Technology, 1998a).

Purpose and Design of 

Sampling

The high concentrations of VOCs in samples 

from monitoring wells prompted the use of PVD 

samplers to identify potential discharges of VOCcontaminated ground water along the shore. Because 

PVD samplers had not been used previously in a 

coastal setting, a secondary goal of this study and a 

companion study in nearby Calf Pasture Point (fig. 22) 

was to determine if PVD samplers can yield useful 

information about discharge points of VOCs along a 

tidally affected shoreline (Lyford and others, 1999b). 

The PVD samplers were installed during March 

16 through 20, 1998, at locations shown in figure 23 

and retrieved on April 1 through 2, 1998. Most samplers (79) were installed during low tide at intervals of 

about 25 ft along about 1,700 ft of shoreline. Samplers 

also were placed at the high-tide level at 20 locations 

for comparison to results from low-tide locations, in 12 

seeps where ground water was apparently discharging 

near the base of the landfill, and at 4 locations on 

mudflats south of the landfill.
38 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 22. Locations of the Allen Harbor Landfill and Calf Pasture Point study areas, Davisville 

Naval Construction Battalion Center Superfund Site, North Kingstown, Rhode Island.

Allen 

Harbor

Landfill

Calf Pasture

Point NARRAGANSETT BAY

ALLEN HARBOR

Spink

Neck

AREA SHOWN

IN FIGURE 23

AREA SHOWN IN

FIGURES 24 & 25

Sanford Road

NAVAL

CONSTRUCTION

BATTALION

CENTER

BOUNDARY

Wetland

RHODE

ISLAND

0 10 MILES

0 10 KILOMETERS

STUDY

AREA

0

0 200

1,000 FEET

METERS

Photographic base (composite) derived from 

U.S. Geological Survey digital orthophotos of portions of 

Wickford and East Greenwich quadrangles, 1:5,000, 

UTM, North American Datum, 1983 

Map modified from Lyford and others, 1999b

71o 71 24'30" o25'

41o

37'30"

41o

37'00"
Allen Harbor Landfill, Davisville Naval Construction Battalion Center Superfund Site, North Kingstown, Rhode Island 39

Figure 23. Directions of ground-water flow in the shallow and deep surficial aquifers, concentrations of volatile organic 

compounds in ground water beneath the Allen Harbor Landfill, December 1995, and concentration of trichloroethene in 

passive-vapor-diffusion samplers installed in tidal-zone sediments along the shoreline of Allen Harbor Landfill, April 1998, 

Davisville Naval Construction Battalion Center Superfund Site, North Kingstown, Rhode Island.
40 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Results

Concentrations of VOCs were detected in 41 

of 115 vapor samplers placed near the Allen Harbor 

Landfill. The most common VOC detected in the samplers was TCE. Other VOCs detected included benzene, toluene, and PCE. Vapor concentrations for total 

VOCs exceeded 100 ppb v at eight locations (fig. 23). 

VOCs were detected at 10 of the 20 high-tide locations 

and at 5 of the 12 seeps. Comparison of the sample 

results at the 20 locations where high-tide and low-tide 

samplers were installed shows that where VOCs were 

detected in the 10 high-tide samples, VOCs were 

detected in only 3 of the companion low-tide samples; 

and where VOCs were not detected in the remaining 10 

high-tide samples, VOCs were detected in 2 of the lowtide samples. The concentrations detected at seeps were 

generally near minimum reporting levels, indicating 

that the seeps were not major discharge areas for 

VOCs. A trace of TCE was detected at one mudflat 

location.

Highest VOC detections were in samplers that 

were placed near well MW09-20I, where high VOC 

concentrations were detected in ground water. The 

extent of the area where VOCs were detected near well 

MW09-20I indicates a VOC plume in ground water 

under the landfill that is at least 300 ft wide at the 

shore. The extent of the plume near well MW09-20I 

had not been mapped previously.

CALF PASTURE POINT, 

DAVISVILLE NAVAL CONSTRUCTION 

BATTALION CENTER SUPERFUND 

SITE, NORTH KINGSTOWN, 

RHODE ISLAND

By Forest P. Lyford, Christine A.P. 

Williams, and William C. Brandon

Description of Study Area

Calf Pasture Point is an area between Allen 

Harbor and Narragansett Bay in North Kingstown, 

Rhode Island (fig. 22), and was part of the former 

Davisville Naval Construction Battalion Center. 

Former waste-disposal activities in the area caused 

contamination of ground water by VOCs (EA 

Engineering, Science, and Technology, 1998b). 

The land-surface altitude in the area shown in 

figure 24 ranges from about 14 ft above sea level near 

well MW07-14D to sea level at the shore line. Depth to 

fractured crystalline bedrock ranges from near land 

surface near monitoring well MW07-14D (fig. 24) to a 

maximum depth of about 70 ft near Narragansett Bay 

at the southeastern corner of figure 24. Bedrock depths 

are about 30 to 40 ft near the shore of Allen Harbor and 

at the entrance channel to Allen Harbor. An upper sand 

layer consisting of fine to very fine sand overlies a 

layer of silt, which, in turn, overlies till or bedrock. The 

silt layer is absent along a north-south-trending till 

ridge between wells MW07-26S and MW07-21S, 

where the upper sand overlies till. The upper sand layer 

includes materials that were dredged from the harbor or 

bay and placed in a former lagoon in the central part of 

the study area and also consists of materials formed by 

recent sedimentation on the southern end of the study 

area (fig. 24) (Church and Brandon, 1999).

Ground water in the upper sand layer flows semiradially outward from a topographic high area near 

well MW07-14D toward Narragansett Bay, Allen 

Harbor, and the entrance channel to Allen Harbor. 

Ground-water-flow direction is generally to the southeast in the deep till aquifer (fig. 24) (Church and 

Brandon, 1999). Vertical hydraulic gradients generally 

are downward, but near well MW07-21S upward gradients have been observed, except during high tide when 

the gradient is zero or downward (EA Engineering, 

Science, and Technology, 1997). Conceptually, shallow 

ground water discharges within the intertidal zone or at 

shallow depths beyond the intertidal zone, and deep 

ground water in till and bedrock discharges in the intertidal zone or further offshore. Data, however, are not 

available for confirmation of discharge points. Shallow 

ground water also appears to discharge to small wetland areas near the entrance channel to Allen Harbor 

(fig. 25).

A plume of VOCs in ground water extends 

from the general area of monitoring well MW07-14D 

towards Narragansett Bay, the entrance channel to 

Allen Harbor, and Allen Harbor (fig. 25). The 

VOCs detected in the plume include vinyl chloride, 

1,2-dichloroethene, PCE, TCE, and 1,1,2,2-tetrachloroethane. Consequently, highest concentrations of VOCs 

in ground water are in wells completed below the silt 

layer at depths of 30 ft or more in till and bedrock. 

In the area of the till ridge where the silt layer is 

absent, VOCs are at shallow depths of 25 ft or less 

(EA Engineering, Science, and Technology, 1998b).
Calf Pasture Point, Davisville Naval Construction Battalion Center Superfund Site, North Kingstown, Rhode Island 41

Figure 24. Potentiometric surfaces and generalized ground-water-flow directions for the shallow and deep surficial 

aquifers, Calf Pasture Point, Davisville Naval Construction Battalion Center Superfund Site, North Kingstown, Rhode 

Island, December 1995.
42 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 25. Concentrations of trichloroethene in passive-vapor-diffusion samplers installed in the tidal-zone 

sediments along the shoreline and in wetland-bottom sediments near the shoreline, Calf Pasture Point, 

Davisville Naval Construction Battalion Center Superfund Site, North Kingstown, Rhode Island, March and 

April 1998.

Probable source area of 

VOCs in ground-water

S

S

S

S

H

H

H

H

H

H

H

MW07-21S

MW07-26S

MW07-14D

Spink Neck

Former Dock

ENTRANCE CHANNEL TO

ALLEN HARBOR

Calf Pasture Point

ALLEN HARBOR

Wetland

area

EXPLANATION

Base traced from U.S. Geological Survey 

orthophoto, 1:12,000, GPS from Trimble Asset 

Surveyor, 1927 North American Datum, 

plume extent from EA Engineering, Science, 

and Technology, 1998b

MW07-21S

71o 71 24'30" o24'45"

41o

37'30"

41o

37'20"

N

Map modified from Lyford and others, 1999b, and 

EA Engineering Services and Technology, 1997

0 200 FEET

0 60 METERS
Otis Air National Guard/Camp Edwards Superfund Site, Johns Pond, Falmouth, Massachusetts 43

Purpose and Design of 

Sampling

The PVD samplers were used at Calf Pasture 

Point to identify possible discharge areas of VOCcontaminated ground water. Other than the study at 

the nearby Allen Harbor Landfill, PVD samplers had 

not been used previously in a coastal setting. Consequently, a secondary goal of the study was to determine 

if PVD samplers can yield useful information about 

areas of VOC discharge along a tidally affected 

shoreline (Lyford and others, 1999b). 

The PVD samplers were installed along the 

shoreline in the area of the VOC plume at low- and 

high-tide locations, in two wetland areas inland from 

the entrance channel to Allen Harbor, and in four seeps 

in or near the intertidal zone. The samplers were 

installed during April 7 through 9, 1998, at 65 locations 

(fig. 25), and retrieved during April 28 through 29, 

1998. The shoreline shown on figure 25 is approximately the extent of water at high tide. Most samplers 

were placed during low tide at intervals of 50 ft along 

about 1,500 ft of shoreline. Because of the limited 

number of samplers available at the time of the study, 

the southwestern side of the study area was given a 

lower priority, and the distances between samplers was 

greater than elsewhere. Samplers were placed at the 

high-tide level at seven locations for comparison to 

results from low-tide locations. 

Results

Concentrations of VOCs were detected in samples from 7 of 37 PVD samplers placed within the 

intertidal zone at Calf Pasture Point and in samples 

from 1 of 24 samplers placed in wetland areas. Concentrations of VOCs were not detected in seepage areas. 

The compound TCE was the only VOC detected, 

except for a trace of PCE detected in one sample 

(Lyford and others, 1999b). Concentrations of TCE 

detected in the PVD samplers ranged from a trace to 

1,900 ppb v (fig. 25). The occurrences of VOCs along 

the shoreline were later confirmed by sampling from 

drive-point wells.

OTIS AIR NATIONAL 

GUARD/CAMP EDWARDS 

SUPERFUND SITE, JOHNS 

POND, FALMOUTH, 

MASSACHUSETTS

By Jennifer G. Savoie and

Denis R. LeBlanc

Description of Study Area

A plume of dissolved VOCs in ground water 

extends 9,000 ft from the site of a storm drain on the 

Otis Air National Guard/Camp Edwards Superfund 

Site, also known as the Massachusetts Military 

Reservation (MMR), to Johns Pond, Mashpee, in the 

Cape Cod area of Massachusetts (Air Force Center for 

Environmental Excellence, 1997, 1998a) (fig. 26). This 

ground-water plume, known as the Storm Drain-5 

(SD-5) plume, primarily consists of TCE with concentrations as high as 66,000 mg/L. Investigations by the 

MMR’s Installation Restoration Program (IRP) suggested that the SD-5 plume was discharging to Johns 

Pond (Air Force Center for Environmental Excellence, 

1998b). The MMR Installation Restoration Program, in 

cooperation with the USGS, sought to confirm that the 

SD-5 plume was discharging to the pond and to 

delineate the extent of the discharge area.

The Cape Cod aquifer near Johns Pond consists 

of about 250 ft of glacial outwash sand and gravel. The 

sediments are texturally uniform laterally and vertically. Johns Pond is a ground-water flow-through 

glacial kettle pond in this sand and gravel outwash 

plain. Ground water generally flows into the pond near 

its western side and discharges back into the ground 

near its eastern side, as indicated by the water-table 

contours on figure 26. 
44 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 26. Locations of the Johns Pond study area and Storm Drain-5 contaminant 

plume, and the altitude of water table (March 1993), Cape Cod, Massachusetts. 
Otis Air National Guard/Camp Edwards Superfund Site, Johns Pond, Falmouth, Massachusetts 45

Purpose and Design of 

Sampling

In this study, PVD samplers were installed in the 

bottom sediments of Johns Pond, to confirm that VOCs 

from the SD-5 plume emanating from the MMR were 

discharging into the pond (Savoie and others, 2000). In 

July 1998, an array of 143 PVD samplers was buried 

about 0.5 ft below the pond bottom in the presumed 

discharge area of the SD-5 plume and left in place for 

about 2 weeks to equilibrate (fig. 27). Divers installed 

samplers at water depths of 5 to 30 ft in Johns Pond. 

The lines of samplers extended a short distance into 

an area of fine grained bottom sediments, presumed 

to be the extent of most ground-water discharge. 

In November 1998, a second more closely spaced 

array of 119 PVD samplers was deployed on the basis 

of interpretation of data collected in August 1998.

Results

Data from the PVD samplers indicated two areas 

of high VOC concentrations. Samples from the first 

area contained TCE and PCE with concentrations in 

vapor as high as 890 and 667 ppb v, respectively 

(fig 27). This discharge area is about 1,000 ft wide, 

extends from 100 to 350 ft offshore, and is interpreted 

to be the discharge area of the SD-5 plume. Lines of 

samplers were long enough, by chance, to define the 

shape of the discharge area. Samples from the second 

area were closer to shore than the discharge area of the 

SD-5 plume and contained vapor concentrations of 

TCE as high as 47,000 ppb v. Ground-water samples 

collected with a drive-point sampler near this location 

confirmed the presence of TCE with concentrations as 

high as 1,100 mg/L. The array of PVD samplers 

deployed in November 1998 was centered around the 

area of high TCE concentrations to map this presumed 

separate plume (fig. 28). The discharge area detected 

with the PVD samplers retrieved in December 1998 

was about 75 ft wide and extended from about 25 to 

200 ft offshore. Vapor concentrations of TCE in this 

area were as high as 42,800 ppb v. Subsequent drilling 

by MMR Installation Restoration Program consultants 

confirmed that the TCE plume appears to be another 

plume that originates northwest of Johns and Ashumet 

Ponds and travels underneath Ashumet Pond (Air 

Force Center for Environmental Excellence, 1999, 

2001) (fig. 29). Because of variations in ground-waterflow patterns laterally and with depth, this plume enters 

the area of Johns Pond from a different direction than 

the SD-5 plume.
46 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Figure 27. Concentrations of trichloroethene plus tetrachloroethene in passive-vapor-diffusion samplers installed in pondbottom sediments adjacent to the Storm Drain-5 contaminant plume, Johns Pond, Cape Cod, Massachusetts, August 1998.
Otis Air National Guard/Camp Edwards Superfund Site, Johns Pond, Falmouth, Massachusetts 47

Figure 28. Concentrations of trichloroethene in passive-vapor-diffusion samplers installed in pond-bottom sediments in 

the zones where high concentrations (greater than 10,000 parts per billion by volume) of trichloroethene were detected 

with passive-vapor-diffusion samplers in August 1998, Johns Pond, Cape Cod, Massachusetts, December 1998.
48 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

NYANZA CHEMICAL WASTE 

DUMP SUPERFUND SITE, 

ASHLAND, MASSACHUSETTS

By Forest P. Lyford, Richard E. 

Willey, and Sharon M. Hayes

Description of Study Area

The Nyanza property, part of the Nyanza 

Chemical Waste Dump Superfund site, is a parcel of 

land in Ashland, Massachusetts (fig. 30), where from 

1917 to 1978, several textile dye manufacturers disposed of various waste products. Some of the wastes 

entered the ground-water system and formed a plume 

that extends to the Sudbury River and a nearby former 

mill raceway (fig. 31) (Roy F. Weston, Inc., 1998). 

The ground-water system includes a surficial 

aquifer of glacial lake deposits and till, and a bedrock 

aquifer of fractured granite. The glacial lake deposits 

range in grain size from silt to coarse sand and gravel. 

The thickness of the fine-grained glacial lake sediments 

increases eastward, and the depth to bedrock increases 

eastward from less than 30 ft in the upstream end of the 

mill pond area to about 80 ft near the upstream end of 

the mill raceway. Most of the Superfund site is on tillcovered bedrock, and the Sudbury River is on silt, sand, 

and gravel (Ebasco Services, Inc., 1991). 

Figure 29. Discharge areas delineated with passive-vapor-diffusion samplers, August and December 1998, and ground-water 

pathways of the Storm Drain-5 plume and trichloroethene plumes, Johns Pond, Cape Cod, Massachusetts.

?

?

Map modified from Savoie and others, 2000 

and assumed pathway of plume provided by 

Air Force Center for Environmental Excellence, 1998–99

ASHUMET 

 POND

ASSUMED PATH OF PLUME

STORM DRAIN-5 PLUME

AREA OF DISCHARGE

NEWLY-FOUND (AUGUST 1998)

DISCHARGE AREA

(DECEMBER 1998)

JOHNS 

 POND

STORM DRAIN-5 

PLUME

(1999)

(1998)

41o38' 05"

41o37' 55"

70o

31' 40" 70o31' 20"

?

EXPLANATION

N

0

0 100 METERS

200 FEET
Nyanza Chemical Waste Dump Superfund Site, Ashland, Massachusetts 49 Figure 30. Location of Nyanza Chemical Waste Dump Superfund Site, passive-vapor-diffusion sampler locations, potentiometric-surface contours for the surficial aquifer, and directions of ground-water flow, Ashland, Massachusetts
50 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England Figure 31. The extent of contaminants in ground water and concentrations of chlorobenzene and trichloroethene detected in passive-vapor-diffusion samples, Nyanza Chemical Waste Dump Superfund Site, Ashland, Massachusetts, February 1999. dam

RAILR

OAD

Y M TR LE

TR S EE T

WATER STREET

PLEASANT

STREET

SUDBURY ROAD

BIRCH LANE

MAIN STREET

E M CT LA F VE. A

OREST F VE A

TILTON AVE.

CH RR E Y TS RE TE

MEGUNKO

ROAD

EP MI R TE RE ROAD

PERIMETER ROAD

GRAVEL ROAD

nabA nod de aR li or da

TROLLEY BROOK ROAD

OOHCS L AOR D

STREET

OC ORD CN

FRONT STREET

CONCORD

CT.

GRANITE

STREET

N

Base map modified from area site plan, Department of the Army New England District Corps of Engineers, Concord, Massachusetts and Weston Managers Designers/Consultants

MILL POND

S U D B U R Y R I V E R S U D B

U RY

R I V E R

R ACEWAY

M I L L

500 FEET 0

100 METERS 0

71o28'30" 71o28'00"

42o15'50"

2o15'30"

EXPLANATION

EXTENT OF GROUND-WATER PLUME WHERE STANDARDS FOR  DRINKING WATER ARE EXCEEDED–Shows area where at least one  chemical in ground water that is believed to originate from Nyanza site  exceeds Massachusetts criteria for drinking water. The location of this  line was determined on the basis of water samples from numerous wells  not shown on this map (Roy F. Weston, Inc., 1999a).PASSIVE-VAPOR-DIFFUSION SAMPLERS–Shows concentrations of  (left side) trichloroethene (TCE) and (right side) chlorobenzene (CB) in  parts per billion by volume (ppb v). Greater than 10,000 Greater than 1,000 to 10,000 Greater than 100 to 1,000 Trace to 100  Not detected above reporting limit of 12 ppb v  for TCE and 40 ppb v for CB or at trace levels Sampler not foundMONITORING WELLS

Map modified from

Lyford and others, 2000
Nyanza Chemical Waste Dump Superfund Site, Ashland, Massachusetts 51

A potentiometric surface map for the surficial 

aquifer (fig. 30) indicates that ground water flows 

northward from the Nyanza property to the Sudbury 

River and Mill Pond and eastward to the Sudbury River 

and former mill raceway downstream from the dam 

that forms Mill Pond (Roy F. Weston, Inc., 1998). A 

plume of contaminants in the surficial and bedrock 

aquifer system follows the ground-water-flow direction 

(fig. 31). Contaminants detected in ground-water 

monitoring wells near the river include the VOCs

1,1,1- trichloroethane, benzene, chlorobenzene, 

cis-DCE, PCE, TCE, and vinyl chloride. Chlorobenzene, TCE, and cis-DCE are the VOCs most commonly 

detected in ground water in the area of the plume. Also 

detected in ground water are mercury and the semi-volatile organic compounds (SVOCs) 1,2,4-trichlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 

1,4-dichlorobenzene (Roy F. Weston, Inc., 1999a). 

Contaminants were not detected in monitoring wells 

near the downstream segment of the mill pond area, 

where water-level data show the pond is a source of 

recharge to ground water (Roy F. Weston, 1999b) 

(fig. 31).

Purpose and Design of 

Sampling

PVD samplers were used near the Nyanza property to accomplish three objectives (Lyford and others, 

2000):

1. Determine if the distribution and concentrations 

of VOCs detected in samples from PVD samplers placed in stream-bottom sediments are 

consistent with the previously mapped distribution of contaminants in ground water near the 

river and former mill raceway.

2. Determine the time needed for VOCs in bottom 

sediments to re-equilibrate after installation of 

the samplers at this site.

3. Determine if PVD samplers might serve as 

alternatives to other sediment-pore-water 

sampling techniques, specifically seepage 

meters and whole sediment samples, to 

characterize the occurrence of VOCs in 

stream-bottom sediments.

To accomplish the first objective, PVD samplers 

were placed at 22 locations along the south bank of the 

Sudbury River in the area of Mill Pond and along the 

Sudbury River and raceway downstream from Mill 

Pond Dam. Samplers were deployed during January 19 

through 20, and retrieved on February 16, 1999. To 

accomplish the second objective, two clusters of three 

PVD samplers each were placed at two sites. One PVD 

sampler from each cluster was retrieved at 1-week 

intervals and transported to USEPA’s Lexington, 

Massachusetts, laboratory for analysis. To accomplish 

the third objective, PVD samplers were placed at locations selected by USEPA to compare analytical results 

with analyses of sediments and pore water extracted 

from seepage meters (Lyford and others, 2000). The 

seepage meters were inverted segments of steel drums 

equipped with a nozzle on the top for extraction of 

water (Roy F. Weston, Inc., 1999a).

Results

The distribution of VOCs in ground water 

detected in samples from PVD samplers agrees well 

with the distribution of contaminants in ground water 

mapped on the basis of samples from monitoring wells 

(fig. 31). Low levels of TCE (less than 25 ppb v) in 

PVD samples at the location farthest upstream indicates that VOCs in ground water may extend somewhat 

further west than the plume shown in figure 31. The 

absence of VOCs in samples from samplers placed at 

the downstream segment of Mill Pond is consistent 

with water-level observations that this section of 

the pond acts as a recharge source to ground water. 

Although chemical data are limited along the Sudbury 

River downstream from the dam, the general absence 

of VOCs in PVD samples indicates that this river reach 

was not a major discharge area for contaminants in 

ground water at the time of the study. The presence of 

VOCs in PVD samples along the mill raceway, however, confirms the mapped extent of the contaminant 

plume in ground water and indicates that the raceway is 

a discharge area for contaminated ground water.

An evaluation of equilibration time for PVD 

samplers in bottom sediments disturbed during installation of samplers indicates that 3 weeks or more may be 

needed in some settings for equilibration. The results 

were inconclusive, however, because changes in river 

stage and discharge may have affected concentrations 

of VOCs. Also, concentrations of VOCs in sediments 

may vary over short distances, and sampling and 

analytical methods are imprecise.
52 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

A comparison of analytical results for PVD 

samplers to analytical results for water from seepage 

meters indicated that concentrations of chlorobenzene 

and TCE correlated well for the two sampling methods. 

A comparison of results from PVD samplers to chemical analyses of sediments indicated that concentrations 

of chlorobenzene and TCE correlated poorly for the 

two methods. At several locations, PVD samplers 

detected VOCs where they were not detected in sediment samples. The apparent absence of VOCs in sediment samples may have resulted from high quantitation 

limits for the analyses.

CENTREDALE MANOR 

RESTORATION PROJECT 

SUPERFUND SITE, NORTH 

PROVIDENCE, RHODE ISLAND

By Peter E. Church, Forest P. 

Lyford, and Anna F. Krasko

Description of Study Area

At the Centredale Manor Restoration Project 

Superfund Site in North Providence, Rhode Island, 

the location of a former chemical company and a 

drum reclamation company, PCBs, dioxin, SVOCs, 

and VOCs have been detected in soils, and VOCs 

have been detected in ground water (A.F. Krasko, 

U.S. Environmental Protection Agency, written 

commun., 1999). The study area is an elongated area 

of about 12 acres along the eastern bank of the 

Woonasquatucket River just downstream of the U.S. 

Route 44 bridge (fig. 32). A former mill raceway that is 

about 1,900-ft long and located several hundred feet 

east of the river forms the approximate eastern boundary of the study area (fig. 33). The southern boundary 

of the study area is 50 ft downstream of the confluence 

of the mill raceway and the Woonasquatucket River, 

about 2,250 ft downstream from the U.S. Route 44 

bridge. A cross channel, about 175-ft long, connects 

the river to the mill raceway about 600 ft upstream 

from this confluence.

Monitoring wells, installed in the northern part 

of the site in March 1999, encountered a top layer of 

fill, 3 to 6 ft thick, composed of silt, sand, gravel, and 

fragments of bricks, concrete, and wood. The fill is 

underlain by 3 to more than 8 ft of sand and gravel,

Figure 32. Locations of the Centredale Manor Restoration 

Project Superfund Site and study area, North Providence, 

Rhode Island.

which, in turn, is underlain by silty, gravelly sand, 

described as till of unknown thickness (A.F. Krasko, 

U.S. Environmental Protection Agency, written 

commun., 1999). The water table at the time these 

wells were drilled ranged from 2.6 to 7.5 ft below land 

surface. A potentiometric surface map is not available 

for this site. From June to November 1999, the USEPA 

collected numerous soil samples in the study area and 

detected dioxin, PCBs, VOCs, and SVOCs. The 

occurrence and distribution of contaminants in ground 

water had not been characterized at the time of this 

study.

.

.
Centredale Manor Restoration Project Superfund Site, North Providence, Rhode Island 53

Figure 33. Concentrations of trichloroethene plus tetrachloroethene in passive-vapor-diffusion samplers 

installed in channel-bottom sediments of the Woonasquatucket River, a former mill raceway, and a cross 

channel, Centredale Manor Restoration Project Superfund Site, North Providence, Rhode Island, September 

1999.
54 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Purpose and Design of 

Sampling

 On September 8 and 9, 1999, 115 PVD samplers 

were installed along the river, raceway, and cross 

channel to identify possible discharge areas of VOCcontaminated ground water and for a preliminary evaluation of the distribution and concentrations of VOCs 

and contaminant pathways in ground water (Church 

and others, 2000). The distance between samplers was 

50 ft, except in reaches of the river and cross channel 

where the USEPA had indicated possible discharge of 

contaminants; in these locations, samplers were placed 

at intervals of 25 ft or less.

On September 21 and 22, 1999, the PVD samplers were retrieved. Sixty of the 62 samplers installed 

in the Woonasquatucket River were retrieved despite 

2 near-flood flows in the 2 weeks after they were 

installed, which is most likely when the 2 samplers 

were lost. Nine of the 19 samplers installed in the lower 

section of the mill raceway were not found. Most likely 

these samplers were either washed away or buried in 

recently re-worked streambed sediments caused by 

high flows. All of the samplers installed in the upper 

section of the mill raceway and in the cross channel 

were retrieved. Target compounds for analysis, selected 

on the basis of soil-sample data, were benzene, ethylbenzene, toluene, meta/para-xylene, ortho-xylene, 

chlorobenzene, PCE, TCE, and 1,1,1-trichloroethane.

Results

VOCs were detected in 58 of the 60 PVD samplers placed in the river, 10 of the 24 samplers in the 

upper mill raceway, 9 of the 10 samplers from the 

lower mill raceway, and 9 of the 10 samplers in the 

cross channel. The compounds TCE and PCE were 

the principal VOCs detected of the nine target compounds, and vapor concentrations of these two compounds were generally less than 100 ppb v (fig. 33). 

Higher vapor concentrations, however, were detected 

along short reaches of these waterways. Vapor concentrations of TCE+PCE in samplers placed in the 

Woonasquatucket River about 500 to 600 ft downstream of the U.S. Route 44 bridge ranged from about 

4,000 to 1,600,000 ppb v (fig. 33). The high vapor concentrations in this short reach, compared to vapor concentrations in river-bottom sediments upstream and 

downstream and in the former mill raceway and cross 

channel indicate that this is a major discharge area of 

contaminated ground water. The compounds TCE and 

PCE were detected in most PVD samplers downstream 

of this discharge area to the outlet of the mill raceway, 

but concentrations of these samples were much lower. 

These concentrations may reflect discharge of less 

contaminated ground water, especially in the approximate 350 ft reach of the river above the mill raceway 

outlet, or may represent mixing of contaminated river 

water with sediment-pore waters. Concentrations of 

TCE+PCE greater than 100 ppb v also were detected in 

the lower part of the upper mill raceway, in the lower 

mill raceway, and in the eastern part of the cross channel, indicating possible discharge areas of contaminated ground water (fig. 33). Nondetect or trace levels 

of VOCs immediately downstream of Route 44 suggest 

minimal contributions of VOCs from upgradient 

sources.

QUALITY-ASSURANCE 

PROCEDURES

Quality-assurance procedures for PVD sampling 

in New England were designed to help explain spurious 

detections of VOCs or anomalously high or low concentrations, if any, that would be difficult to explain on 

the basis of available site information. For all studies 

reported here, the primary objective was to identify 

possible discharge areas for VOCs in ground water. For 

this objective, the main quality concern was detections 

in PVD samplers where VOCs were not present and 

nondetections where VOCs were present. To help evaluate the concern that the sampling or analytical technique might cause detections of VOCs where they were 

not present, samplers were placed in areas where contaminants were not likely, such as upstream from or 

upgradient from mapped contaminant plumes in 

ground water. For all studies, numerous samples indicated that VOCs were not present in detectable quantities where they were unlikely to be present in ground 

water.

Duplicate samples were collected to help 

address the concern of false VOC detections where 

they were not present or false nondetections where they 

were present. Analyses of numerous samples that indicated concentrations below or above detection limits 

were confirmed with duplicate samples. Of the 437 
Quality-Assurance Procedures 55

duplicate-samples analyses (number of duplicate samples times the number of target compounds), a VOC 

was not detected above reporting limit in either sample 

in 343 duplicate samples; a VOC was detected above 

the reporting limit in both samples in 83 duplicate samples; a VOC was detected above the reporting limit in 

one sample but not the other in 11 duplicate samples 

(table 3). In 6 of the 11 exceptions, where a VOC was 

detected in one of the samples, but was not in the other, 

the highest concentration was less than 100 ppb v.

The concentrations of VOCs detected in PVD 

samplers for some sites provided useful information 

about the relative magnitude of concentrations of 

VOCs that might be expected at the ground-water and 

surface-water interface. For this use of the data, results 

from duplicate samples generally provided assurance 

that concentrations detected in samples were reasonable for that point sampled. A relative percent difference of 30 percent is commonly used to evaluate 

measurement performance in screening methods. A 

summary of relative percent differences between duplicate samples where a VOC was detected in both samples is shown in table 4. The relative percent difference 

for most duplicate samples analyzed for chlorinated 

VOCs (PCE, TCE, and chlorobenzene) were within 30 

percent. For unknown reasons, however, a lower percentage of samples analyzed for petroleum compounds 

were within the 30 percent criteria for relative percent 

difference.

Trip blanks and equipment blanks also were used 

in some places to determine if contaminants were introduced during transport or during capping of sampler 

vials. No VOCs were detected in any of these samples 

except for a low concentration of toluene in one sample. The detection of toluene did not compromise the 

result observed for that site

.

Table 3. Number and distribution of duplicate samples from the nine study sites in New England

[Number of duplicate sample analyses is the number of duplicate samplers deployed multiplied by the number of target compounds]

Study site

Number of

duplicate

sample

analyses

Concentration

detected above

reporting limit

in both samples

Concentration

not detected

above reporting

limit in both

samples

Concentration

detected above

reporting limit

in only one

sample

Eastern Surplus Company Superfund Site, 

Meddybemps, Maine ............................................................... 12 4 8 0

McKin Company Superfund Site, Gray, Maine........................... 12 8 4 0

Nutmeg Valley Road Superfund Site, Wolcott and 

Waterbury, Connecticut ........................................................... 56 8 45 3

Baird & McGuire Superfund Site, Holbrook, 

Massachusetts .......................................................................... 215 33 175 7

Allen Harbor Landfill, Davisville Naval Construction 

Battalion Center Superfund Site, North Kingstown, 

Rhode Island............................................................................ 24 1 23 0

Calf Pasture Point, Davisville Naval Construction

Battalion Center Superfund Site, North Kingstown, 

Rhode Island............................................................................ 6 0 6 0

Otis Air National Guard/Camp Edwards Superfund 

Site, Johns Pond, Falmouth, Massachusetts ............................ 36 12 23 1

Nyanza Chemical Waste Dump Superfund Site, 

Ashland, Massachusetts........................................................... 20 6 14 0

Centredale Manor Restoration Project Superfund 

Site, North Providence, Rhode Island ..................................... 56 11 45 0

Total ............................................................................................. 437 83 343 11
56 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

SUMMARY AND 

CONCLUSIONS

Passive-vapor-diffusion (PVD) samplers are 

designed for detecting and delineating areas of VOCcontaminated ground water discharging into surfacewater bodies. A PVD sampler consists of an empty 

glass vial sealed inside a polyethylene membrane 

tubing that is permeable to many VOCs of interest, 

such as petroleum and chlorinated compounds, but is 

not permeable to water. Samplers are buried in the 

bottom sediment of surface-water bodies, at or below 

the transition zone between surface water and ground 

water; and VOCs in the adjacent pore water, if present, 

diffuse through the polyethylene tubing and equilibrate 

with concentrations of air in the empty vial. 

Applications of PVD samplers at and near nine 

hazardous-waste sites in New England have demonstrated the effectiveness of this sampling method in 

several hydrologic settings, including rivers and 

streams, ponds, wetlands, and coastal shorelines 

through a variety of bottom sediments including sand, 

silt, clay, organics, gravel, and cobbles. Areas of VOCcontaminated ground-water discharge from known 

ground-water plumes were confirmed or refined 

with PVD samplers at all nine sites. Areas of VOCcontaminated ground-water discharge from previously 

unknown ground-water plumes were identified with 

PVD samplers at the following Superfund Sites: 

Eastern Surplus Company in Maine; Baird & McGuire 

and Otis Air National Guard/Camp Edwards (Johns 

Pond) in Massachusetts; and Centredale Manor 

Restoration Project in Rhode Island.

The samplers should remain in place until sufficient time has elapsed for the pore water to recover 

from the environmental disturbances caused by sampler deployment and for the samplers to attain sufficient VOC concentrations to fulfill the data-quality 

objectives of the study. If the data-quality objective 

is to locate a VOC-contaminated ground-waterdischarge area, then the samplers may be recovered 

before they have completely equilibrated, if they have 

accumulated sufficient VOC concentration to identify 

the contaminant-discharge area. Field studies suggest 

that this can be accomplished after a deployment 

period of 8 days or less, and in as little as 24 hours 

in some environments.

Spacing of samplers and selection of sampler 

location are also important in achieving the dataquality objectives. A sampling strategy for detecting 

plumes of VOCs in ground water or refining plume 

boundaries typically requires preliminary knowledge 

about potential sources of VOCs and a conceptual 

model of pathways for contaminants in ground water. 

Sampling should extend well upstream and downstream from likely discharge areas. The studies in New 

England have demonstrated that plumes typically discharge well beyond a riverbank or shoreline on the 

plume side of the water body. In fact, samplers placed 

at the edge of the water body may not detect a plume. 

In small streams a few feet wide, samplers placed along 

the center of a stream are typically sufficient to map 

plumes in ground water. Most plumes in New England 

hydrologic settings are at least 100 ft wide where they 

enter a surface-water body, so a spacing of 50 to 100 ft 

should be adequate to detect the presence of VOCs. In 

large water bodies such as rivers and ponds, a grid of 

samplers spaced 50 to 100 feet apart would typically 

detect the presence of VOCs. If the sampling goal is to 

characterize local variations in concentrations of 

VOCs, a shorter spacing may be needed.

The ability of PVD samplers to detect areas 

of discharging VOC-contaminated ground water 

depends on a variety of factors affecting contaminant 

discharge. These factors include the location and 

Table 4. Relative percent differences of volatile organic 

compound (VOC) concentrations in duplicate samples 

where a VOC was detected above the reporting limit in both 

duplicate samples from the nine study sites in New England

Volatile

organic

compound

Number of

duplicate

samples

Percent of relative

percent differences of

concentrations in

duplicate samples

Less than 

or equal to

30 percent

Greater than 

30 percent

Tetrachloroethene....... 13 92 8

Trichloroethene .......... 37 81 19

Chlorobenzene ........... 2 100 0

Benzene...................... 10 60 40

Ethylbenzene.............. 6 50 50

meta/para-Xylene ...... 7 43 57

ortho-Xylene .............. 4 75 25

Toluene....................... 4 75 25
Summary and Conclusions 57

lithologic heterogeneity of the discharge area, the 

orientation of the stream channel relative to the 

ground-water contamination, the offshore distance 

of the contaminant-discharge area, the potential temporal nature of the discharge-area location and discharging concentrations, and potential removal of VOCs by 

bed-sediment micro-organisms. 

Two studies in New England (Lyford and others, 

2000; Savoie and others, 2000) included co-located 

PVD and water-filled polyethylene bags described by 

Vroblesky (2001) to determine if concentrations of 

VOCs in pore water can be predicted from concentrations observed in PVD samplers. In theory, Henry’s 

Law can be used to convert concentrations of VOCs in 

vapor to concentrations in water. Results of the two 

studies cited indicated that the use of PVD samplers for 

this purpose might be appropriate. Also needed, however, are temperature data measured with commercially 

available temperature probes for pore water at the sampling depth, and equilibration times of PVD samplers 

for the sediments in which the sample is obtained. In 

some settings, direct collection of pore-water samples, 

such as with small-diameter probes (Henry, 2000), may 

be more efficient than use of PVD samplers.

Several other types of information are useful for 

interpreting results from PVD sampling. It is helpful 

to know concentrations of VOCs in surface water. It 

is commonly assumed that the VOCs that discharge 

from ground water to surface water quickly volatilize 

to the atmosphere. In practice, however, VOCs persist 

downstream from a source and can compromise 

results of PVD sampling. Sampling of surface water 

upstream and downstream of the study area and at several points along a stream, depending on the length of 

the stream reach, is useful for interpreting PVD data 

from sediment-pore water. Surface-water data might 

be collected by suspending a sampler in surface water 

near the bottom of the water body or collecting water 

samples for head-space analysis on site or for standard 

laboratory analyses offsite.

It is also helpful to collect hydraulic head data at 

piezometers. Concurrent water levels in piezometers 

and surface water at the time of sampler deployment or 

retrieval will help determine if VOCs are discharged 

with ground water or accumulated in sediments from 

other sources. Continuous stage and ground-waterlevel data are also needed to detect changes in hydrologic conditions, such as a flood wave, that may affect 

VOC concentrations in sediments. Subsequent sampling may be desirable if hydrologic conditions 

changed appreciably during the sampling period.

Knowledge gained and lessons learned from the 

nine New England studies may be useful for others 

considering the application of PVD samplers. Results 

from these studies have provided insights on groundwater-flow patterns near surface-water bodies. Variations of VOC concentrations over short distances 

within areas of ground-water discharge were detected 

at several sites, which suggests local variations in contaminants at the contaminant source and possible local 

variations in ground-water-flow patterns. Discharge of 

VOC-contaminated ground water has been detected 

across the widths of rivers and streams. In one case, 

continued flow beneath the floodplain at a bend in the 

river resulted in VOCs being discharged through the 

bottom sediments to the opposite bank further downstream. Results at one site reinforced concepts about 

gaining and losing reaches in a mill-pond area and 

indicated that a former mill raceway was the principal 

discharge area for contaminated ground water downstream from the mill pond. Numerous detections of 

VOCs within a tidal zone near a landfill supported 

the concept that much of the shallow ground-water 

discharges in the tidal zone. The absence of VOCs in 

another tidal zone where VOCs are known to be 

present at depth suggests that the deep ground water 

discharges further offshore. The effect of surficial geology on ground-water discharge to surface-water bodies 

was observed at one site where the area of groundwater discharge from a deep surficial aquifer was 

affected by the lateral extent of an overlying confining 

lacustrine deposit.

Concentrations of VOCs in PVD samplers 

placed in river-bottom sediment downstream from the 

likely extent of a plume, but also in areas where VOCs 

were detected or are likely to be in surface water, may 

indicate an exchange of water between the surface 

water and bottom sediments. In this situation, surfacewater sampling is needed, as well as the use of PVD 

samplers in the bottom sediments of the surface-water 

body. This additional sampling will help determine if 

VOCs in surface water have affected the concentrations 

of VOCs detected with the PVD sampler.

The absence of VOCs in PVD samplers does not 

exclude the possibility that VOCs are present in ground 

water. For at least two studies, VOCs were not detected 
58 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

in some areas where they were known to be present in 

ground water. Local flow conditions may have diverted 

the discharge of contaminated ground water in these 

areas, or surface water may have been the principal 

source of water in bottom sediments. Where VOCs are 

suspected but not detected in PVD samplers, groundwater sampling may be needed for confirmation. The 

absence of VOCs at the ground-water/surface-water 

interface in areas of known ground-water contamination may indicate that surface water is a source of 

recharge. It may also indicate that discharge points for 

contaminated ground water are outside the area of 

investigation. This information is useful for further 

characterization of ground-water contamination and 

contaminant pathways.

Results from PVD samplers provide a qualitative 

assessment of VOC concentrations in ground-water 

plumes where they enter surface-water bodies. A fair 

correlation was observed between concentrations of 

VOCs in PVD samples and concentrations in water 

from co-located seepage meters. Several uncertainties, 

however, preclude estimating actual VOC concentrations in ground water from concentrations in vapor 

from PVD samplers. These uncertainties include equilibration times, variations in concentration over short 

lateral distances, variations in concentrations vertically 

(particularly at shallow depths), variations in temperatures at the ground-water and surface-water interface, 

and changing hydrologic conditions that affect groundwater-flow patterns and flow rates. These uncertainties, 

however, are not critical to successful application of the 

technique if the data-quality objective is simply to 

identify the presence of VOCs. 

Quality-assurance procedures for PVD sampling 

help explain questionable detections of VOCs or unexpected high or low concentrations. For all studies in 

New England, numerous samples indicated that VOCs 

were not present in detectable quantities where they 

were unlikely to be present in ground water. Analysis 

of duplicate samples helped address the concern of 

false VOC detections where VOCs are not present, or 

false nondetections where VOCs are present. Numerous duplicate samples confirmed concentrations below 

or above detection limits. Duplicate samples also provided assurance that concentrations detected were reasonable for the point sampled. The relative percent 

difference for most duplicate samples analyzed for 

chlorinated VOCs were within 30 percent. For petroleum compounds, a lower percentage of samples analyzed were within the 30 percent criteria for relative 

percent difference. In some areas, analysis of trip 

blanks and equipment blanks helped determine if contaminants were introduced during transport or during 

capping of sample vials. VOCs were not detected in 

any of these samplers, except for a low concentration of 

toluene in one sampler, which did not compromise the 

result observed for that site.

Unexplored uses of PVD samplers include evaluation of chemical transformations at the groundwater/surface-water interface. These transformations 

can be evaluated by targeting degradation products 

during analysis of vapor or water, and by identification 

of areas of high concentrations of chemicals of environmental concern, such as semi-volatile organic compounds and metals, that are co-located with VOCs in 

ground water. After equilibration times for a particular 

setting are determined, PVD samplers also may help 

monitor concentrations of VOCs. Deploying PVD samplers could provide an alternative to installing wells, 

when a permanent well would present a safety hazard, 

such as to boats and swimmers, or where permanent 

wells would be subject to damage by vehicles or ice. 

Similarly, PVD samplers could be useful for studying 

how VOC concentrations change as hydrologic 

conditions change.

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62 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

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Appendix 1. Laboratory and Field Testing of

Passive-Vapor-Diffusion Sampler Equilibration

Times, Temperature Effects, and Sample Stability

By Don A. Vroblesky

Appendix 1 65

Laboratory and field tests were conducted to 

determine the time required for the vapor in the airfilled vials of the PVD samplers to equilibrate with 

concentrations of VOCs in the pore water of the adjacent sediment, and to determine the stability of VOC 

concentrations between the time of sample recovery 

and sealing of the sample vials. For the laboratory and 

field tests, the PVD samplers consisted of a 20-mL 

serum vial enclosed in a heat-sealed, 1.5-in. diameter 

LDPE tube. The vial was arranged such that a single 

layer of polyethylene was held tightly in place over the 

vial opening. The tubing was secured to the vial by a 

self-locking nylon tie. The assembly then was placed 

inside a second tube and heat sealed, trapping a minimum of air. Samplers used in the field were attached 

with self-locking nylon ties to a wire surveyor flag to 

mark the sampling site and to facilitate sampler 

recovery.

Upon recovery of the PVD samplers, the outer 

tube was cut open, leaving the inner tubing intact. 

A vial cap with a Teflon-coated stopper then was 

crimped onto the vial and inner bag. Vapor samples 

were obtained from the PVD samplers by inserting a 

syringe needle tip through the Teflon-coated stopper 

beneath the vial cap and extracting the vapor with a 

gas-tight syringe. Analysis of the the vapor was analyzed by photoionization detection with a Photovac 

10SPlus gas chromatograph.

Equilibration Times and 

Temperature Effects

Equilibration times of PVD samplers under laboratory conditions were examined at 21°C and 10°C. For 

the test at 21°C, groups of three PVD samplers were 

added to 480-mL water-filled test jars spiked with a 

mix of VOCs at concentrations of approximately 20 to 

100 μg/L each of cis-1,2-dichloroethene (cis-DCE), 

benzene, TCE, toluene, and PCE, in February 1998. 

The jars were stored at a 21°C for the duration of the 

test. For the test at 10°C three PVD samplers were 

added to each of fourteen 1.9-L test jars spiked with a 

mix of benzene (570 μg/L), toluene (520 μg/L), TCE 

(430 μg/L), and PCE (500 μg/L), in June 2001. The 

test jars were maintained at approximately 10°C 

by storing them in an incubator. Water temperatures in 

the jars were measured at each sampling time and 

ranged from 7.6 to 11.3°C (average of 10.2°C). The 

water-filled jars in both tests contained no headspace.

An additional test was done to compare differences in equilibrium concentrations at various temperatures. Standards of toluene and PCE were added to 

water in a 40-L container. The PVD samplers were 

placed in 1.9-L jars in groups of three, and the jars were 

filled with test water by submerging and capping the 

jars underwater in the 40-L container. The jars were 

stored at different temperatures. At various times, one 

jar from each temperature treatment was opened, the 

temperature was measured, the PVD samplers were 

capped, and a water sample was collected for toluene 

and PCE laboratory analysis. Vapor samples from the 

PVD samplers were analyzed by headspace analysis. 

Water temperatures ranged from 0.2 to 4.1°C (average 

of 1.4°C) in the coldest treatment, from 7.9 to 10.8°C 

(average of 9.5°C) in the next coldest treatment, and 

from 19.4 to 24.6°C (average of 22.4°C) in the roomtemperature treatment. Concentrations in water ranged 

from 210 to 310 μg/L of toluene and 110 to 340 μg/L of 

PCE.

Recovery of the PVD samplers at each sampling 

time consisted of opening the jar, removing the PVD 

samplers, cutting open the external LDPE bag, and 

sealing the PVD samplers with crimp-type caps with 

Teflon-faced seals. The test at 21°C involved 10 sampling times over approximately 59 hours (table 1A), 

the test at 10°C involved 13 sampling times and 1 

duplicate over approximately 222 hours (table 1B), and 

the test at 3 temperatures involved 6 sampling times 

and 1 duplicate sample over 456 hours (table 1C). 

In addition, the USGS conducted relatively shortterm tests of PVD samplers deployed in streambed sediments in areas of VOC-contaminated ground-water 

discharge to examine sampler equilibration dynamics 

under field conditions. For these tests, the samplers 

were deployed in different environments. Site1 was in 

Coastal Plain sands at the Savannah River Site, South 

Carolina, in an area with a relatively high upward 

hydraulic gradient (0.3 ft/ft). The sediment at site 1 had 

a relatively large hydraulic conductivity of 21 to 65 ft/d 

(Nichols, 1993; Nichols and others, 1995; Phifer and 

others, 1995). Site 2 was in silty saprolite downgradient 

from a former waste-drum disposal site in a part of the 

stream with a relatively low upward hydraulic gradient 

(0.02 ft/ft). 
66 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Table 1A. Average concentrations and standard deviations of volatile organic compounds in passive-vapor-diffusion samplers 

over time at 21 degrees Celsius under laboratory conditions in 480-milliliter test jars with spiked concentrations of less than 100 

micrograms per liter

[cis-DCE, cis-1,2-dichloroethene; TCE, trichloroethene; ppb, parts per billion]

Time,

in hours

Number of 

samplers

Average concentrations, in ppb by volume Standard deviation, in ppb by volume

cis-DCE Benzene TCE Toluene cis-DCE Benzene TCE Toluene

0 3 0 0 0 0 0 0 0 0

0.75 3 158 223 118 146 23 77 52 75

1.75 3 431 498 171 110 124 175 73 40

2.75 3 654 939 271 218 159 393 103 119

5.75 3 687 1,054 297 276 192 300 71 50

10.75 3 1,416 2,058 492 565 315 669 209 316

23.75 3 1,970 3,101 813 913 14 64 26 27

31.75 3 1,880 3,044 802 975 68 121 66 122

51.75 3 1,853 2,923 732 929 54 86 29 52

58.75 3 1,705 2,747 695 879 34 58 10 24

Table1B. Average concentrations and standard deviation of volatile organic compounds in passive-vapor-diffusion samplers 

over time at 10 degrees Celsius under laboratory conditions in 1.9-liter test jars with spiked concentrations ranging from 430 to 

570 micrograms per liter

[PCE, tetrachloroethene; TCE, trichloroethene; D, Duplicate test jar; NA, not applicable; ppb, parts per billion]

Time, in 

hours

Number of 

samplers

Average concentrations, in ppb by volume Standard deviation, in ppb by volume

Benzene TCE Toluene PCE Benzene TCE Toluene PCE

0 3 0 0 0 0 0 0 0 0

2.25 3 150 303 0 0 10 35 0 0

5.25 3 823 1,065 333 69 359 514 90 15

9.25 3 1,880 2,130 1,185 334 1,655 1,451 540 81

14.25 3 6,166 4,999 2,853 700 3,877 2,762 1,177 165

28.75 2 20,265 14,395 9,787 2,432 318 389 896 144

35.25 2 21,180 14,725 9,737 2,347 1,414 2,539 655 166

57.25 1 25,450 24,060 15,110 4,223 NA NA NA NA

78.25 3 31,227 33,523 20,360 6,179 2,177 4,393 767 313

102.25 3 31,990 35,293 22,480 7,054 652 1,979 1,644 612

150.25 2 31,220 34,275 23,320 7,867 438 1,025 184 522

150.25 D 1 32,150 37,140 21,430 7,229 NA NA NA NA

222.25 3 31,543 35,253 21,900 7,465 957 1,303 1,763 584
Appendix 1 67

Hydraulic gradients at each site were determined 

by driving 1-in-diameter steel pipes into the streambed 

to depths of 1.5 and 3 ft. A bolt loosely seated into the 

downward end of the pipes prevented sediment from 

moving up into the pipe as it was driven into the sediment. The bolt then was driven out of the pipe to allow 

water to enter. After a few hours of equilibration, the 

water levels in the pipes were measured relative to the 

stream stage outside the pipes. These water levels provided an approximate measurement of the upward 

hydraulic gradient. At each field site, approximately 20 

to 30 PVD samplers were buried in an area of approximately 6 ft2. The samplers were recovered in groups of 

three at various times over approximately 50 hours.

Equilibration time for PVD samplers under field 

conditions depends on the time required by the PVD 

sampler to equilibrate with ambient water, and the time 

required for the contaminant distribution in pore water, 

disturbed by installation of the sampler, to return to 

ambient conditions. Laboratory tests presented here 

provide information regarding the time required by the 

PVD sampler to equilibrate with ambient water. Field 

data for this and other investigations involving various 

types of in-situ samplers can provide a better understanding of the time required for sediment-pore-water 

concentrations to equilibrate after disturbances caused 

by sampler deployment. 

Temperature is one primary factor affecting the 

equilibration time of VOC movement across a polyethylene membrane. At 21°C under laboratory conditions, 

the time required for concentrations of cis-DCE, benzene, TCE, toluene, and PCE to stabilize was approximately 24 hours (fig. 1A, table 1A). At 10°C under 

laboratory conditions, concentrations of benzene, TCE, 

toluene, and PCE appeared to require about 102 hours 

to equilibrate (fig. 1B, table 1B). Equilibration times, 

therefore, increase as temperature decreases. This 

increase in equilibration time with decreasing temperature is consistent with the general trend previously 

shown for sampling major ions and nutrients with dialysis samplers (Carignan, 1984). In these studies, equilibration times ranged from approximately 15 days in a 

warm (20–25°C) environment, and approximately 20 

days in a cold (4–6°C) environment.

Table 1C. Ratio of concentrations from passive-vapor-diffusion sampler to aqueous-phase concentrations for toluene and 

tetrachloroethene over time at various temperatures under laboratory conditions in 1.9-liter test jars containing 210 to

310 micrograms per liter of toluene and 110 to 340 micrograms per liter of tetrachloroethene

[ppb v to μg/L, ratio of parts per billion by volume to micrograms per liter; °C, degrees Celsius; --, no samples]

Hours

Ratio of passive-vapor-diffusion to aqueous-phase concentrations (ppb v to μg/L)

Toluene Tetrachloroethene

22.4°C 9.5°C 1.4°C 22.4°C 9.5°C 1.4°C

0 0.0 0.0 0.0 0.0 0.0 0.0

24 76.9 11.3 15.5 14.4 3.9 2.2

72 116.1 73.4 19.7 60.1 35.9 6.6

192 107.3 62.7 21.0 67.6 35.9 11.7

336 105.3 60.0 27.9 81.3 39.0 17.3

336 100.3 55.8 -- 69.8 46.7 --

456 103.5 49.8 23.4 68.4 33.9 17.2
68 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Temperatures also change the equilibrium distribution of VOCs between the aqueous and vapor phase. 

At cold temperatures, there is less of a tendency for volatilization than at warmer temperatures. For the same 

aqueous concentration, therefore, higher concentrations 

will be detected in PVD samplers at warm temperatures 

than at cold temperatures (fig. 1C, table 1C).

In contrast, differences in VOC concentrations 

between tests or sites theoretically should not produce 

different equilibration times. The concentration gradient between the inside and outside of the polyethylene 

membrane does affect the diffusion flux, as evidenced 

by Fick’s Law; however, although a steeper concentration gradient results in an increased diffusion rate, the 

required amount of solute transfer is larger than in a 

lower concentration gradient. In effect, the equilibration time is the same for both situations. This fact can 

be seen in the formula for halftime of chemical uptake 

of organic compounds across a polyethylene membrane 

in semipermeable membrane devices (SPMDs):

t0.5u = -ln 0.5 (Kow VL/RS), 

where t0.5u is the halftime to equilibration, Kow is the 

octanol-water coefficient, VL is the volume of the lipid 

sorbent, and RS is the volume of water sampled by the 

SPMD per day and is independent of concentration 

(Huckins and others, 1997). 

Field tests for this investigation demonstrate 

that equilibration times can vary among field sites. At 

site 1 in South Carolina, the TCE concentrations in the 

PVD samplers approximately stabilized after about 

12 to 24 hours (fig. 1D, table 1D). At site 2 in South 

Carolina, however, the TCE concentrations still were 

increasing at 47 hours (fig. 1D, table 1D). A field test in 

Massachusetts found that PVD samplers in sediments 

of the Sudbury River appeared to require 3 weeks or 

more to equilibrate (Lyford and others, 2000). These 

differences in equilibration times can result from a variety of factors. At site 1, the rate of water movement 

past the samplers was substantially larger than the rate

Figure 1A. Changes in concentrations of volatile organic compounds in passive-vapor-diffusion 

samples over time at 21 degrees Celsius under laboratory conditions in a mixed solution of volatile 

organic compounds with aqueous concentrations less than 100 micrograms per liter. CONCENTRATION, IN PARTS PER BILLION BY VOLUME

0 10 20 30 40 50 60

0

1,000

2,000

3,000

4,000

5,000

cis-1,2-Dichloroethene

Benzene

Trichloroethene

Toulene

HOURS
Appendix 1 69

past the slower equilibrating samplers at site 2, as 

evidenced by the differences in permeability and 

hydraulic gradient (fig. 1D). The surface water 

introduced into the excavated sampler holes would 

have been more rapidly replaced by discharging ground 

water at site 1 than at site 2. Additionally, site 1 was 

sampled in early September, and site 2 was sampled 

two months later, in November. Colder water 

temperatures in November may have contributed to the 

decrease in equilibration time. The samplers from the 

Sudbury River in Massachusetts were recovered from 

fine-grained sediment in February 1999, in water that 

was substantially colder than at either of the South 

Carolina sites.

An important concept to remember in considering the length of equilibration time for field deployment, however, is that PVD samplers typically are used 

as a reconnaissance tool in surface-water sediments to 

locate areas of discharging ground water contaminated 

with VOCs. For this use, the mere presence or absence 

of target VOCs in samplers can provide practical 

information. At the field locations tested in South 

Carolina, the PVD samplers showed considerable concentrations of the target VOCs within 24 hours or less 

(fig. 1D). Despite the apparent lack of equilibration, the 

PVD samplers in the Sudbury River showed considerable concentrations by the first retrieval (8 days). 

Although the PVD samples had not equilibrated at all 

of the sites, the data from all of the sites were adequate 

to meet the objective of mapping contaminant-discharge areas. These data suggest that a deployment 

period of 8 days or less is adequate to provide data sufficient to locate major VOC discharge areas beneath 

surface water, and as little as 24 hours is sufficient at 

some sites. 

If it is important for the data-quality objective 

that the PVD samples must have reached equilibrium 

at the time of sampler recovery, then the samplers 

may need to remain in place longer than 8 days, 

depending on the rate of ground-water movement and

Figure 1B. Changes in concentrations of volatile organic compounds in passive-vapor-diffusion 

samples over time at 10 degrees Celsius under laboratory conditions in a mixed solution of volatile 

organic compounds with aqueous concentrations ranging from 430 to 570 micrograms per liter.

HOURS

0 50 100 150 200 250

0

10,000

20,000

30,000

40,000

50,000

CONCENTRATION, IN PARTS PER BILLION BY VOLUME

Benzene

Tricholorethene

Toluene

Tetrachloroethene 
70 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

the ground-water temperature. Some insight into equilibration times can be gained by examining passivediffusion-bag (PDB) samplers, which are water-filled 

polyethylene diffusion samplers. Under laboratory conditions at 21°C, the PDB samplers equilibrate more 

slowly (approximately 48 hours; Vroblesky, 2000) than 

PVD samplers (approximately 24 hours); therefore, the 

field equilibration times of PVD samplers probably are 

no longer than those for PDB samplers under similar 

field conditions. One field investigation showed adequate equilibration of PDB samplers to aquifer TCE

and carbon tetrachloride within 2 days in a highly permeable aquifer (Vroblesky and others, 1999). In other 

investigations, PDB samplers recovered after 14 days 

were found to be adequately equilibrated to chlorinated 

VOCs (Obrien & Gere Engineers, Inc., 1997a, 1997b; 

Hare, 2000); therefore, the equilibration time was 14 

days or less under those field conditions. Because it 

appears that 2 weeks of equilibration time probably is 

adequate for many applications sin permeable formations, a minimum PVD-equilibration time of 2 weeks is 

recommended for discharge areas in sandy sediment. 

Figure 1C. Ratio over time of (A) toluene and (B) tetrachloroethene gas 

concentrations by volume (parts per billion) in passive-vapor-diffusion samplers to 

aqueous concentrations by mass (210 to 310 micrograms per liter of toluene and 110 

to 340 micrograms per liter of tetrachloroethene) in a test solution containing the 

diffusion samplers in 1.9-liter jars at average temperatures of 22.4, 9.5, and 1.4 

degrees Celsius.

0 100 200 300 400 500

0

20

40

60

80

100

120

140

HOURS

0 100 200 300 400 500

0

20

40

60

80

100

22.4 oC

9.5 oC

1.4 oC

A. Toluene

B. Tetrachloroethene

TEMPERATURE, IN DEGREES CELSIUS

VAPOR CONCENTRATION, IN PARTS PER BILLION

AQUEOUS CONCENTRATION, IN MICROGRAMS PER LITER
Appendix 1 71

Equilibration of PVD samplers in fine-grained 

sediment may take longer than 2 weeks, as shown 

by the test in the Sudbury River (Lyford and others, 

2000). Equilibration times for PVD samplers in poorly 

permeable sediment have not yet been determined. 

A confounding factor in determining equilibration 

times in such conditions is that flow conditions and 

possibly plume concentrations can vary with time and 

space, and these variations may be reflected in the 

PVD-sampler concentrations. 

In summary, if the data-quality objective is to 

locate areas of VOC-contaminated ground-water 

discharge, then a deployment period of 8 days or less is 

adequate to provide data sufficient to locate major 

VOC discharge areas beneath surface water, and as 

little as 24 hours is sufficient at some sites. If it is 

important for the data-quality objective that the PVD 

samplers must have reached equilibrium at the time of 

sampler recovery, then the samplers may need to 

remain in place for about 2 weeks in sandy sediment 

and possibly longer than 3 weeks in poorly permeable 

sediment at cold temperatures.

Sample Stability

Laboratory tests also were conducted to determine the diffusion loss of VOCs in PVD samplers 

between the time of sampler recovery and sealing of 

the sampler vials. The samplers were allowed to equilibrate for 2 weeks in a water-filled container having 

mixed VOCs. The samplers then were removed from 

the water and allowed to stand at 21°C for various time 

intervals over a period of hours before capping. The 

vapor samples then were analyzed by photo-ionization 

gas chromatography.

Concentrations of benzene, TCE, and toluene in 

uncapped PVD samplers at 21°C did not substantially 

decrease over 60 minutes between sampler recovery 

and capping the sampling vials. These data suggest that 

VOC concentrations within the uncapped PVD samplers are relatively stable for at least 1 hour at 21°C 

under laboratory conditions. Under field conditions, 

however, abrasions and other factors may adversely 

affect the membrane. Consequently, it is strongly recommended that PVD samples be capped and sealed 

immediately upon recovery.

Figure 1D. Changes in trichloroethene concentrations over time in passive-vapordiffusion samples from contaminated ground-water discharge areas in South 

Carolina in (Site 1) Coastal Plain sediments and (Site 2) Piedmont sediments with 

differing sediment types and vertical hydraulic gradients.

HOURS

0 5 10 15 20 25 30 35 40 45 50 55

0

200

400

600

800

1,000

0 5 10 15 20 25 30 35 40 45 50 55

0

2,000

4,000

6,000

8,000

 Iv = 0.3

A. Coastal Plain

B. Piedmont

SITE 2. Silty saprolite

 Iv

TRICHLOROETHENE, IN PARTS PER 

 = 0.02

BILLION BY VOLUME

SITE 1. Unconsolidated sands
72 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

Table 1D. Average concentrations and standard deviations of trichloroethene over time in passive-vapor-diffusion samplers in 

bottom sediment of streams at contaminated ground-water-discharge areas in the Coastal Plain (site 1) and the Piedmont 

(site 2) of South Carolina, 1998

[TCE, trichloroethene; ppb, parts per billion; NA, not applicable]

Site 1 Site 2

Hours after 

deployment

Number

of samples

TCE concentration,

in ppb by volume Hours after 

deployment

Number

of samples

TCE concentration, 

in ppb by volume

Average Standard

deviation Average Standarddeviation

0 1 0 NA 0 1 0 NA

.08 3 5 4 .08 3 0 0

.5 3 307 60 1 3 0 0

1 3 378 146 2 3 6 6

2 3 815 117 3 3 47 19

3 2 1,431 313 4.6 3 92 21

5 3 1,208 270 9 3 136 61

7 3 1,601 516 12.75 3 400 156

10 3 4,710 1,103 17 3 286 120

24 3 5,693 1,300 23 3 586 127

31 3 5,002 1,167 41 3 647 78

47 2 5,019 1,758 50.5 3 894 91
Appendix 2. Field Screening of Volatile Organic

Compounds Collected with Passive-Vapor-Diffusion 

Samplers with a Gas Chromatograph

By Scott Clifford, U.S. Environmental Protection Agency

Appendix 2 75

1.0 Summary of Method

Field screening with a portable gas chromatograph (GC) provides tentative identification and estimated concentrations of volatile organic compounds 

(VOCs) in air samples. This screening technique can 

provide quick and reliable results to assist in important 

onsite decision making. An aliquot of the air/vapor 

sample is injected into a calibrated GC equipped with a 

photoionization detector and electron capture detector. 

Results indicating VOC detections and estimated concentrations are displayed on a chart recorder, a portable 

computer screen, or other data-collection system. 

Retention times, the time since injection of the sample 

into the GC to the time peak responses are recorded, 

are used for compound identification. The peak 

heights, or areas, are used to estimate concentrations of 

the identified compounds. Reporting levels (RL) can 

vary depending upon instrument performance and settings, or can be set on the basis of data quality objectives. Typical achievable reporting levels for many 

VOCs of interest are shown in table 2A. Concentrations 

are in units of parts per billion by volume (ppb v).

2.0 Scope and Application

The procedure described here is applicable 

to chemists performing screening for VOCs in air 

samples collected with passive-vapor-diffusion (PVD) 

samplers.

3.0 Definitions

3.1 FIELD DUPLICATES (FD1 and FD2):

Two separate samples collected at the same time and 

place under identical circumstances and treated exactly 

the same throughout field and laboratory procedures. 

Analyses of FD1 and FD2 give a measure of the precision associated with sample collection, preservation, 

and storage, as well as with laboratory procedures.

3.2 HEADSPACE: Air above water standard in 

sample vial.

3.3 LABORATORY DUPLICATE (LD1 and 

LD2): Two injections from the same sample. The analyses of LD1 and LD2 give a measure of the precision 

associated with the laboratory procedure.

3.4 LABORATORY REAGENT BLANK 

(LRB): An aliquot of reagent water or other blank 

matrix that is treated exactly as a sample including 

exposure to all glassware, equipment, solvents, 

reagents, internal standards, and surrogates that are 

used with other samples. The LRB is used to determine 

if method analytes or other interferences are present 

in the laboratory environment, the reagents, or the 

analytical apparatus.

3.5 FIELD BLANK: A PVD sampler left out in 

the ambient air (for example, attached to a tree) for the 

duration of the sample-collection period.

3.6 STOCK STANDARD SOLUTION: A concentrated solution containing one or more method analytes prepared in the laboratory by use of using assayed 

reference materials or purchased from a reputable 

commercial source.

3.7 WORKING STANDARD SOLUTION: A 

solution of several analytes prepared in the laboratory 

from stock standard solutions and diluted as needed to 

prepare calibration solutions and other needed analyte 

solutions.

3.8 SECONDARY STANDARD: A standard 

from another vender or a different lot number that is 

used to check the primary standard used for estimating 

concentrations.

4.0 Health and Safety 

Warnings

4.1: The toxicity or carcinogenicity of each 

reagent used in this method has not been precisely 

determined; therefore, each chemical should be treated 

as a potential health hazard. Exposure to these reagents 

should be reduced to the lowest possible level. The 

laboratory is responsible for maintaining a current 

awareness file of the Occupational Safety and Health 

Administration (OSHA) regulations regarding the safe 

handling of the chemicals specified in this method. A 

reference file of data-handling sheets should be made 

available to all personnel involved in these analyses. 

Use these reagents in a fume hood whenever possible; 

and if eye or skin contact occurs, flush with large 

volumes of water. 

4.2: Always wear safety glasses or a shield for 

eye protection, wear protective clothing, and observe 

proper mixing when working with these reagents.
76 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

4.3: Some method analytes have been tentatively 

classified as known or suspected human or mammalian 

carcinogens. Pure standard materials and stock standard solutions of these compounds should be handled 

with suitable protection to skin and eyes.

5.0 Personnel Qualifications

5.1: The analyst should have at least a 4-year 

degree in a physical science.

5.2: The analyst should be trained at least 1 week 

and have a working knowledge of this method and 

quality control before initiating the procedure.

5.3: All personnel shall be responsible for 

complying with all quality-assurance/quality-control 

requirements that pertain to their organizational/ 

technical function.

6.0 Equipment and Supplies

6.1: Gas chromatograph equipped with a photoionization detector (PID) in series with an electron capture detector (ECD), and an analytical column capable 

of separating target analytes.

6.2: Data-collection system (for example, a chart 

recorder, intergrator or a portable computer).

6.3: Syringes: steel barrel, volume of 250 μL to 

500 μL; 2 in., 25-gauge needle.

6.4: Vials: 40 mL volatile organic analysis 

(VOA) vials with Teflon lined septum caps.

7.0 Preparation of Air and 

Aqueous Standards

7.1: The air standard for each target analyte is 

the headspace above a l0 μg/L aqueous standard at 

approximately 0 to 1°C for each target analyte. Aqueous standards are prepared with target analyte concentrations of 10 μg/L and are stored on ice in 40 mL VOA 

vials with no head space. When ready for use, 10mL of 

the aqueous standard are withdrawn from the vials to 

produce a headspace from which vapors are analyzed 

and serve as air standards. The vials are then placed 

into an ice bath in a cooler with the septa side facing 

downward, and left to equilibrate for approximately 

30 minutes. Because the concentration of the volatile 

organic compounds in the head space was calibrated at 

approximately 0 to l°C, the working standards must be 

maintained at the same temperature.Vapor-standard 

concentrations of volatile organic compounds commonly detected with passive-vapor-diffusion samplers 

in the headspace of a 10 μg/L aqueous standard at 

approximately 0 to l°C have been determined through 

in-house experimentation and are shown in table 2B.

Table 2A. Typical achievable reporting limits for volatile 

organic compounds commonly detected in passive-vapordiffusion samplers from a gas chromatograph equipped with 

a photoionization detecter and an electron capture detector

Volatile organic compound

Reporting limit,

in parts per billion

by volume

Benzene ............................................... 10

Ethylbenzene ....................................... 50

meta/para-xylenes ............................... 50

ortho-xylene ........................................ 80

Toluene ................................................ 40

Chlorobenzene..................................... 50

Trichloroethylene ................................ 10

Tetrachloroethylene ............................. 2

1,1-Dichloroethene.............................. 10

cis-1,2-Dichloroethene ........................ 15

trans-1,2-Dichloroethene .................... 10

1,1,1-Trichloroethane .......................... 6
Appendix 2 77

7.2: Aqueous standards are made weekly from a 

methanol stock solution and volatile organic-free water, 

and stored in a 40-mL VOA vial on ice with no head 

space. 

7.3: The methanol stock standard and secondary 

stock standard are replaced every 3 months.

7.4: The aqueous working and secondary standards are good for 7 days provided these standards are 

stored on ice with no headspace.

8.0 Instrument Operation

Gas chromatographs are available from many 

commercial sources. Operation of any particular 

gas chromatograph should be in accordance with 

procedures supplied by the manufacturer.

9.0 Instrument Calibration

Calibration for analysis of vapor samples collected with PVD samplers generally consists of taking 

a 200 μL volume of the headspace in the 10 μg/L 

aqueous, 0 to 1°C standard with a 250 μL steel-barrel 

syringe with a 2 in., 25-gauge needle, and injecting it 

into the injection port of the GC. The actual vapor 

concentration is listed in table 2B for selected 

compounds. This single point calibration is completed 

by analyzing a blank, which is obtained from the 

headspace above a volatile organic-free water sample 

in a 40 mL VOA vial.

10.0 Analysis

10.1: Insert the syringe needle into the PVDsampler septum and use the plunger to flush the syringe 

barrel three times. After flushing, pull the plunger up to 

the 200 μL point on the barrel and remove the needle 

from PVD sample.

10.2: Insert the syringe needle into the GC 

injection port, and push the needle through the septum 

until the barrel comes up against the injection port, 

immediately push the plunger with a quick action, 

remove needle from injection port, and turn on the 

data-collection system.

10.3: Record the following information:

l. start of run,

2. sample number,

3. sample volume,

4. attenuation or gain, and

5. other relevant comments.

10.4: The order in which of a group of samples is 

analyzed is as follows:

10.4.1: Calibration Standard—Inject a 

200-μL sample of 10-μg/L standard at 0 to 1°C headspace into the GC. Keep standard peaks at approximately 50 percent scale or more, if possible, by 

adjusting the attenuation or gain.

10.4.2: Repeat 10-μg/L standard to check 

for reproducibility. Standard chromatograms should 

have compound peak heights within 15 percent of each 

other and retention times should be identical.

10.4.3: Inject the secondary standard for 

confirmation. The acceptance criteria is within 20 

percent of the true value.

Table 2B. Vapor concentrations of volatile organic 

compounds commonly detected with passive-vapor-diffusion 

samplers in the head space of a 10 micrograms per liter 

aqueous standard at approximately 0 to 1 degree Celsius

Volatile organic compound Concentration, in parts 

per billion by volume

Benzene ............................................... 151

Ethylbenzene ....................................... 145

meta/para-xylenes ............................... 136

ortho-xylene ........................................ 112

Toluene ................................................ 159

Chlorobenzene..................................... 70

Trichloroethylene ................................ 142

Tetrachloroethylene ............................. 201

1,1-Dichloroethene.............................. 554

cis-1,2-Dichloroethene ........................ 90

trans-1,2-Dichloroethene .................... 202

1,1,1-Trichloroethane .......................... 330
78 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England

10.4.4: Clean air blank—Inject a 200-μL 

sample of clean air into the gas chromatograph with the 

attenuation set at the same level or lower than the level 

at which samples will be run. Blank clean air is taken 

from the headspace above volatile organic-free water in 

a 40-mL VOA vial.

10.4.5: Samples—Inject 200-μL sample 

volume into the GC at the same attenuation level at, or 

lower than the attenuation at which the standard was 

run. If contaminant levels on the chromatograms are 

off-scale, adjust the attenuation or gain to decrease 

instrument response. If the chromatographic peaks 

are still off-scale, rerun the samples with a smaller 

injection volume.

10.4.6: Repeat 10-μg/L calibration standard 

every 10 samples and at the end of the sample batch to 

check the calibration and reproducibility. Standard 

chromatograms should have compound peak heights 

within 20 percent of each other, and retention times 

should be identical.

11.0 Identification and 

Estimated Concentration

11.1: Identify compounds present in a sample by 

matching retention times of peaks in the sample chromatogram to the retention times of standard peaks 

determined at site. 

11.2: Concentrations are estimated by a peakheight or peak-area comparison. For example, if the 

l0-μg/L aqueous-standard head space had a benzene 

peak height of 32 units from a 200-μL injection with 

instrument attenuation at 2, an identified benzene peak 

l2 units high from a 200-μL sample injection with 

instrument attenuation at 2 would represent a sample 

benzene concentration of 57 ppb v.

32 units = 12 units

*151 ppb v X ppb v

X = 57 ppb v Benzene

* See Air Standard Section 7.1 (table 2B)

12.0 Interferences

12.1: Method interferences may be caused by 

contaminants in solvents, reagents, glassware, and 

other sample-processing hardware that lead to discrete 

artifacts and (or) elevated baselines in the chromatograms. All of these materials must routinely be demonstrated to be free from interferences under the 

conditions of the analysis by running laboratory and 

field method blanks.

12.2: Matrix interferences may be caused by 

contaminants that coelude with the target compounds. 

The extent of matrix interferences will vary considerably from source to source. A different column or 

detector may eliminate this interference.

12.3: Contamination by carry-over can occur 

whenever high-level and low-level samples are sequentially analyzed. To reduce carry-over, a VOA free water 

blank should be analyzed following an unusually concentrated sample to assure that the syringe is clean.

13.0 Quality Control

Quality-control procedures and acceptance criteria listed below, along with corrective actions, are 

shown in table 2C.

13.1: A blank and a 1-point standard is used for 

instrument calibration. Initially, run a 10-μg/L standard 

(at 0–1°C) to determine retention times and response
Appendix 2 79

factors of instrument. Repeat the 10-μg/L standard to 

check the reproducibility. Acceptance criteria for this 

initial calibration is less than 15 percent difference 

from the first standard injection. 

13.2: Laboratory blanks are analyzed at the initial calibration and periodically to be sure of no carry 

over from previous injections. Technical judgement is 

used to determine frequency of blank-sample analysis. 

Acceptance criteria is no target-compound peaks 

greater than one-half the reporting level. 

13.3: A second source standard containing some 

compounds of interest is analyzed daily to verify calibration standard. Acceptance criteria is less than 20 

percent difference of the true value.

13.4: A standard is run at least every 10 samples 

and at the end of the sample batch to update the instrument calibration. Acceptance criteria is less than 20 

percent difference from previous standard.

13.5: Run field and laboratory duplicates every 

twenty samples. Acceptance criteria is a relative percent difference between the two values of less than 

30 percent for field duplicates and 20 percent for 

laboratory duplicates.

13.6: Field blanks are analyzed at least once per 

survey. Field blanks are PVD samplers left out in ambient air (for example, attached to a tree) for the duration 

of the sample-collection period and are retrieved and 

analyzed the same day(s) as samples. Acceptance criteria is no target-compound peaks greater than one-half 

the reporting level.

14.0 Data and Records 

Management

14.1: All work performed for the analyses of 

samples must be entered into a field logbook. These 

data are then reviewed and verified for precision, accuracy, and representativeness by the project chief or 

project manager with analysis of the quality-assurance 

data.

14.2: The samples analyzed are logged into a 

laboratory-information-management system.

14.3: Chromatograms generated are saved and 

filed in a project folder.

1Acceptance criteria defined by technical judgement.

Table 2C. Quality controls, acceptance criteria, and corrective actions

[DQO, data-quality objective; RL, reporting limit; RPD, relative percent difference; <, less than]

Quality-control item Frequency Acceptance criteria Corrective action

Initial calibration Daily, before samples < 15 percent difference 

from the first standard1

Inject another standard, check system

Blank Daily, every batch < 1/2 of RL1 Repeat blank injection, prepare a new blank, check system, 

increase RLs depending on DQOs

Second source standard Daily, every batch < 20 percent difference 

from true value1

Inject another standard, repeat initial calibration, check 

system

Continuing calibration Every 10 samples and 

after the last sample

< 20 percent difference 

from previous 

standard1

Inject another standard, repeat initial calibration, check 

system

Field duplicate Every 20 samples < 30 percent RPD1 Repeat injection

Laboratory duplicate Daily, every 20 samples < 20 percent RPD1 Repeat injection, run another duplicate

Field blank At least one per survey <1/2 of RL1 Repeat injection. Evaluate data using

 technical judgement
80 Guidance on Use of Vapor-Diffusion Samplers to Detect VOCs in Ground-Water-Discharge Areas, and Applications in New England
Appendix 2 81