Evaluation of Passive Diffusion Bag Samplers in 

Selected Wells at the Naval Surface Warfare 

Center, Louisville, Kentucky, July 1999 to 

January 2000

By Don A. Vroblesky, Matthew D. Petkewich, and

Clifton C. Casey

U.S. Geological Survey

Water Resources Investigations Report 01–4163

Prepared in cooperation with the

SOUTHERN DIVISION NAVAL FACILITIES ENGINEERING COMMAND

Columbia, South Carolina

2001
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Use of trade, product, or firm names in this publication is for descriptive purposes only and 

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

For additional information Copies of this report can be 

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

720 Gracern Road Box 25286

Columbia, SC 29210-7651 Denver, CO 80225

888-ASK-USGS

Additional information about water resources in South Carolina is available on the 

World Wide Web at http://sc.water.usgs.gov
Contents III

CONTENTS

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

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

Site History ...................................................................................................................................................................... 3

Hydrogeology................................................................................................................................................................... 3

Methods...................................................................................................................................................................................... 3

Results and Discussion .............................................................................................................................................................. 6

Summary .................................................................................................................................................................................. 15

References................................................................................................................................................................................ 16

FIGURES

1. Map showing location of observation wells used in this investigation at the Naval Surface Warfare Center, 

Louisville, Kentucky ......................................................................................................................................................... 2

2. Graph showing comparison of benzene, toluene, ethyl benzene, and total xylenes concentrations in passive diffusion 

bag samplers and in pumped samples, well 1-NW-MW24-S, Naval Surface Warfare Center, Louisville, 

Kentucky, January 2000 .................................................................................................................................................. 12

TABLES

1. Well-construction and passive diffusion bag sampler information for wells used in this investigation, Naval Surface 

Warfare Center, Louisville, Kentucky............................................................................................................................... 4

2. Water levels and saturated intervals in wells, Naval Surface Warfare Center, Louisville, Kentucky ................................... 5

3. Summary of passive diffusion bag sampler results, Naval Surface Warfare Center, Louisville, Kentucky.......................... 6

4. Comparison of volatile organic compound concentrations in passive diffusion bag samples and pumped samples, 

September 1999 and January 2000, and historical sampling results, Naval Surface Warfare Center, Louisville, 

Kentucky ........................................................................................................................................................................... 7
IV Contents

CONVERSION FACTORS, ABBREVIATIONS, ACRONYMS, 

AND VERTICAL DATUM

Chemical concentration: In this report, chemical concentration in water is expressed in metric units as 

milligrams per liter (mg/L) or micrograms per liter (μg/L). 

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 Sea Level Datum of 1929.

Multiply By To obtain

Length

inch (in.) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

Volume

gallon (gal) 3.785 liter

Flow

foot per day (ft/d) 0.3048 meter per day

foot per year (ft/yr) 0.3048 meter per year

L liter

μg microgram

mL milliliter

BRAC Base Realignment and Closure Program

LNAPL light non-aqueous phase liquid

LDPE low-density polyethylene

MTBE methyl-tert-butyl ether

NSWC Naval Surface Warfare Center

PDB passive diffusion bag

USGS U.S. Geological Survey

VOA volatile organic analysis

VOC volatile organic compound
Introduction 1

Evaluation of Passive Diffusion Bag Samplers in Selected 

Wells at the Naval Surface Warfare Center, Louisville, 

Kentucky, July 1999 to January 2000

By Don A. Vroblesky1, Matthew D. Petkewich1, and Clifton C. Casey2

ABSTRACT

Passive diffusion bag samplers were tested in 11 

wells at the Naval Surface Warfare Center, Louisville, 

Kentucky, by comparing the volatile organic compound concentrations obtained from passive diffusion 

bag samplers to volatile organic compound concentrations obtained by pumping the wells. The wells were 

screened in poorly permeable formations, including 

overburden, shale, and limestone. In five of the tested 

wells containing detectable volatile organic compound 

contamination, the data suggest that the diffusion samplers accurately reflected ambient contaminant concentrations (wells 1-NEC-15-P, 1-NEC-MW17-S, 1-NEMW23-S, 1-NW-MW24-S, and 1-NW-MW24-P). 

Comparison of a third well (1-NEC-MW34-S), in 

which the passive diffusion bag samplers produced 

higher concentrations than the pumped sample, is less 

certain because the passive diffusion bag sampler had 

passed through a layer of light non-aqueous phase 

liquid during deployment, suggesting the possibility of 

carryover contamination. In two wells (1-NE-MW23-P 

and 1-NEC-MW15-S), it was unclear whether concentrations obtained by using the passive diffusion bag 

samplers adequately represented in situ concentrations 

because the comparison of concentrations obtained by 

using the samplers and the pump was inconsistent 

between sampling events and/or between volatile 

organic compounds. In one well (1-NEC-MW34-P), 

the methodologies matched poorly, with volatile 

organic compound concentrations obtained by using 

the passive diffusion bag sampler substantially lower 

than those obtained by using the pump. Two of the 

tested wells (1-NW-MW6-I and 1-SE-MW13-I) contained no detectable contaminants in water obtained 

from either method.

Data from wells where multiple passive diffusion bag samplers were deployed showed the lowest 

volatile organic compound concentrations adjacent to 

the vuggy limestone and higher volatile organic compound concentrations deeper in the limestone, supporting colloidal-borescope data that indicate the 

vuggy limestone is not a zone that supplies water 

to the wells.

INTRODUCTION

Ground-water contamination by a variety of 

compounds is present at the Naval Surface Warfare 

Center (NSWC), also known as the Naval Ordnance 

Station, Louisville, Ky. (fig. 1). The facility is part of 

the U.S. Department of Defense Base Realignment 

and Closure (BRAC) program. The NSWC is on 

approximately 144 acres within the southern limits 

1U.S. Geological Survey, Columbia, S.C.

2Southern Division Naval Facilities Engineering 

Command, Charleston, S.C.
2 Evaluation of Passive Diffusion Bag Samplers in Selected Wells at the Naval Surface Warfare Center, Louisville, Kentucky, 

July 1999 to January 2000

00 25 50 75 100 METERS

100 200 300 400 500 FEET

BuildingRoadRailroadObservation well or well clusterand name of well

EXPLANATION

Kentucky

Lexington

Frankfort

Louisville

65

75

71 64

24

Naval Surface

Warfare Center

A

B

C

D

E

F

G

H

W

L

V

1-SE-M

W13-I

1-NW-M

W6-I

1-NW-M

W24-P

1-NW-M

W24-S

1-NE-M

W23-P

1-NEC-M

W15-S 1-NEC-M

W15-P

1-NEC-M

W34-P

1-NEC-M

W34-S

1-NEC-M

W17-S

1-NE-M

W23-S

1-NW-MW24-P1-NW-MW24-S

Figure 1. Location of observation wells used in this investigation at the Naval Surface Warfare Center, Louisville, Kentucky.
Methods 3

of Louisville, Jefferson County, approximately 7 miles 

(mi) south of downtown Louisville, and approximately 

1 mi west of Louisville International Airport. 

The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of the Navy, Southern 

Division Naval Facilities Engineering Command, 

investigated the potential for use of low-density polyethylene (LDPE) passive diffusion bag (PDB) samplers 

(Vroblesky and Hyde, 1997) as an alternative methodology for collecting ground-water volatile organic 

compound (VOC) samples. The standard technique 

used at the site to collect ground-water samples is a 

pumping method using purge-and-sample technology. 

The investigation involved side-by-side comparisons 

of contaminant concentrations obtained by using PDB 

samplers to concentrations obtained by using groundwater pumps in 11 wells. This reports presents the 

findings of that investigation. 

Site History

Since 1941, the NSWC has manufactured, 

overhauled, and produced weapons systems needed by 

combat vessels of the U.S. Navy. Various hazardous 

chemicals, including petroleum hydrocarbons, have 

been released to the soil and ground water as a result 

of past disposal activities and accidental spills and 

releases. At least three sumps may have breached a 

shale confining unit separating the shallow overburden 

water-bearing zone from the underlying limestone 

aquifer. Free-phase petroleum was found in the limestone aquifer at several locations on the facility, as well 

as at Auburndale, Ky., approximately 1.5 mi south of 

the facility (Charles J. Taylor, U.S. Geological Survey, 

written commun., 1996). Hydrocarbon characterization 

(fingerprinting) showed the petroleum to be crude oil 

(Environmental Liability Management, Inc, 1999), and 

its widespread occurrence suggests a natural source.

Hydrogeology

The site hydrogeology has been investigated 

extensively by consultants and the U.S. Geological 

Survey (Charles J. Taylor, U.S. Geological Survey, 

written commun., 1996). Unless otherwise noted, all 

information contained in this section is derived from 

Tetra Tech NUS, Inc. (2000). 

The subsurface at NSWC Louisville is characterized by a shallow overburden, ranging in thickness 

from about 7 feet (ft) in the eastern and northeastern 

part of the facility to about 30 ft in the western and 

southwestern part of the facility. The sediment consists predominantly of clays and silty clay with lesser 

amounts of sand and gravel. In most places at the 

facility, the overburden is underlain by an organic 

shale confining unit, averaging about 10 ft thick and 

locally absent in the extreme western and southwestern areas of the facility. Limestone underlies the shale 

and overburden. A 1- to 5-ft thick vuggy zone of 

moldic porosity is present in the upper part of the 

limestone, approximately 1 ft below the shale contact, 

and the zone is stained with crude oil in parts of the 

facility as well as in some offsite wells (Charles J. 

Taylor, U.S. Geological Survey, written commun., 

1996). Colloidal borescope measurements in the wells 

implied that the vuggy zone does not transmit water 

(Aqua VISION, 1999). 

In general, all of the strata are poorly permeable. 

The overburden is composed of clay to silty clay. 

The average horizontal hydraulic conductivity of the 

overburden, based on slug tests, is approximately 

1.6 feet per day (ft/d), and these data in combination 

with measured hydraulic gradients and estimated 

porosity, imply that the ground-water velocity is about 

1.46 to 3.28 feet per year (ft/yr). Although no aquifer 

tests were done in the shale, the lithology, sparseness 

of fractures, and literature values for hydraulic conductivity suggest a seepage velocity of about 0.12 ft/yr. 

Bedrock packer tests in the limestone showed average 

horizontal hydraulic conductivities ranging from 

1.3×10-1 to 1×10-3 ft/d. 

METHODS 

Ground-water samples were collected from 11 

wells (fig. 1) to compare VOC results obtained from 

PDB samplers to results obtained by purging and 

sampling the wells (table 1). PDB samplers used in the 

wells consisted of a 1.5-inch (in.)-diameter low-density 

polyethylene (LDPE) tube heat-sealed at both ends and 

containing deionized water. The samplers were deployed 

and recovered for two separate sampling events. During 

the first sampling event, samplers were deployed in 

July and recovered in September 1999. During the 

second sampling event, samplers were deployed in two 

wells in September and in five wells in December 1999 
4 Evaluation of Passive Diffusion Bag Samplers in Selected Wells at the Naval Surface Warfare Center, Louisville, Kentucky, 

July 1999 to January 2000

with all samplers recovered in January 2000. A LDPE 

mesh placed on the outside of the samplers provided 

protection against abrasion. The samplers were positioned at the target horizons by attachment to a nylon 

weighted line. Target horizons were chosen to coincide with geologic features, such as the vuggy zone, to 

approximate the center of a saturated interval or to 

provide vertical distribution data.

Samplers were recovered by using the attached 

weighted line. Water was removed from the diffusion 

sampler by cutting it open and gently pouring the 

water contents into 40-milliliter (mL) volatile organic 

analysis (VOA) vials, making sure that no headspace 

remained. Water in the vials was preserved with 

hydrochloric acid to lower the pH to approximately 

2, and the samplers were then stored on ice. Chemical 

analyses were conducted at a commercial laboratory 

using U.S. Environmental Protection Agency Method 

8260b (U.S. Environmental Protection Agency, 1999).

During the first test (September 1999), the 

USGS purged and sampled nine wells immediately 

following recovery of the PDB samplers. Very slow 

purging [less than 80 milliliters per minute (mL/min)] 

with a peristaltic pump removed nearly all the water in 

wells 1-NE-MW23-P, 1-NW-24-P, 1-NEC-17-S, 

1-NEC-15-P, and 1-NEC-34-P; the wells were allowed 

to partially recover prior to collecting the samples. 

Each well was sampled by pumping a water sample 

from the target horizon with a peristaltic pump or a 

Bennett positive-displacement pump.

The remaining four tested wells 1-NE-MW23-S, 

1-NW-MW24-S, 1-NEC-MW15-S, and 1-SE-MW13-I 

were not completely purged during the first test in an 

attempt to obtain water in the direct vicinity of the 

diffusion samplers. Wells 1-NE-MW23-S and 1-NWMW24-S were purged at a low rate (approximately 

100 mL/min) for 30 minutes, and the pump was turned 

off. Well 1-NE-MW23-S was allowed to recover for 

Table 1. Well-construction and passive diffusion bag sampler information for wells used in this investigation, 

Naval Surface Warfare Center, Louisville, Kentucky

Well Zone

Well 

depth

 (feet)

Well 

diameter 

(inches)

Screen 

length 

(feet)

Number of 

samplers 

installed

Date 

deployed

Date 

recovered

Days of 

equilibration

1-NEC-MW15-P Overburden 12.78 4 5 1 7/28/99 9/22/99 56

1-NE-MW23-P Overburden 11.17 4 5 1 7/28/99 9/20/99 54

1 12/15/99 1/11/00 27

1-NW-MW24-P Overburden 11.93 4 5 1 7/28/99 9/21/99 55

1-NEC-MW34-P Overburden 10.4 4 5 1 7/28/99 9/23/99 57

1 12/15/99 1/12/00 28

1-NW-MW6-I Shale 17.97 2 3 1 7/8/99 9/22/99 56

2 12/15/99 1/12/00 28

1-SE-MW13-I Shale 21.56 2 5 1 7/28/99 9/23/99 56

1-NEC-MW15-S Limestone 40.64 4 10 1 7/28/99 9/22/99 56

2 9/23/99 1/12/00 111

1-NEC-MW17-S Limestone 38.68 4 10 1 7/28/99 9/23/99 57

1-NE-MW23-S Limestone 45.13 4 20 1 7/28/99 9/21/99 55

3 9/23/99 1/11/00 110

1-NW-MW24-S Limestone 37.77 4 15 1 7/28/99 9/21/99 55

3 12/15/99 1/11/00 27

1-NEC-MW34-S* Limestone 38.26 4 15 1 12/15/99 1/12/00 28

* Contained light non-aqueous-phase liquid.
Methods 5

2 hours, and water was collected from the vicinity of 

the sampler by using a peristaltic pump. The pumped 

samples from well 1-NW-MW24-S were collected 

after purging for 20 minutes with less than 0.1 ft of 

drawdown, within 2 hours following PDB-sampler 

recovery. The well was sampled by using a Bennett 

pump because the depth to water exceeded the peristaltic pump capacity. 

Wells 1-NEC-MW15-S and 1-SE-MW13-I also 

were sampled after purging at a low rate for 30 minutes. 

The aquifer at well 1-NEC-MW15-S was very poorly 

permeable. After pumping the well slowly (78 mL/min) 

for 1 hour and 42 minutes, virtually all the pumped 

water continued to come from well storage, as determined by comparing the calculated change in water volume within the well to the measured volume of water 

pumped out of the well. The pumping rate was 

increased, lowering the water level in the well a total of 

22 ft. The pump was then turned off, and the well was 

allowed to remain undisturbed for 1 hour and 17 minutes; however, the water level showed no change. Thus, 

the sampling data indicated that the well is poorly connected to the aquifer, and water samples collected from 

this well 1-NEC-MW15-S by the purge-and-sample 

method, should be regarded as questionable. Similarly, 

most of the water pumped from well 1-SE-MW13-I 

seems to have been from aquifer storage.

During the second test, a commercial contractor 

sampled the wells within 1 or 2 days of PDB-sampler 

recovery by the USGS. Well purging was accomplished 

by using a 2-in. diameter submersible positive-displacement pump for the recharging bedrock wells or a disposable bailer for the low-volume shallow wells or lowyielding deeper wells. The samples were collected after 

evacuating the well casing or after purging three casing 

volumes of water by using a pump or bailer. The water 

samples obtained using PDB samplers were shipped 

with and analyzed by the same laboratory as the samples 

collected by the conventional approach for each well. 

In five of the tested wells (1-NEC-MW17-S, 

1-NEC-MW15-P, 1-NW-MW24-P, and 1-NECMW34-P), the length of the saturated water column 

within the well screen was less than 3 ft (table 2). 

Wells having short saturated intervals are of concern 

because of the potential for the PDB samplers to be 

exposed above the water column.

PDB sampler data showed a close match between 

replicate samples. The PDB sampler at well 1-NECMW23-S showed concentrations [53 micrograms per 

liter (μg/L) benzene, 18 μg/L toluene, 9 μg/L 2-butanone, 18 μg/L ethyl benzene, and 42 μg/L total xylenes] 

equal to or within a few micrograms per liter of concentrations obtained from a duplicate sample collected 

from the same sampler (54 μg/L benzene, 18 μg/L 

toluene, 9 μg/L 2-butanone, 17 μg/L ethyl benzene, 

and 39 μg/L total xylenes). 

Table 2. Water levels and saturated intervals in wells, Naval Surface Warfare 

Center, Louisville, Kentucky

[Depth to water is below top of casing; NS, no sample]

Well

September 1999 January 2000

Depth 

to 

water 

(feet)

Length of 

water 

column 

in well 

(feet)

Saturated 

screen 

interval 

(feet)

Depth 

to 

water 

(feet)

Length of 

water 

column 

in well 

(feet)

Saturated 

screen 

interval

(feet)

1-NEC-MW15-P 11.09 1.69 1.69 NS NS NS

1-NE-MW23-P 5.98 5.19 5 6.28 4.89 4.89

1-NW-MW24-P 10.88 1.05 1.05 NS NS NS

1-NEC-MW34-P 7.75 2.65 2.65 7.57 2.83 2.83

1-NW-MW6-I NS NS NS 7.07 10.9 3

1-NEC-MW15-S NS NS NS 18.07 22.57 10

1-SE-MW13-I 6.93 14.63 5 NS NS NS

1-NEC-MW17-S 37.37 1.31 1.31 NS NS NS

1-NE-MW23-S 10.94 34.19 20 9.91 35.22 20

1-NW-MW24-S 23.01 14.76 14.76 20.7 17.07 15

1-NEC-MW34-S NS NS NS 5.82 32.44 15

* Data from Tetra Tech NUS, Inc. (2000).
6 Evaluation of Passive Diffusion Bag Samplers in Selected Wells at the Naval Surface Warfare Center, Louisville, Kentucky, 

July 1999 to January 2000

RESULTS AND DISCUSSION 

Most of the tested horizons at NSWC Louisville 

were low yielding. In general, caution should be exercised when sampling low-yielding aquifers by conventional methods or by the PDB-sampler method. When 

using a pump, if the pumping rate exceeds the recharge 

rate, then part of the pumped water is from well storage rather than directly from the formation. Moreover, 

there is potential for volatilization losses by trickling 

flow if the well is pumped until the water level declines 

below sources of contaminated-water recharge and 

then allowed to recover before sampling. When using 

the PDB method in a low-yielding aquifer, caution 

should be exercised because of the potential that the 

rate of volatilization loss in the wellbore may exceed 

the rate of VOC inflow to the wellbore from the aquifer. Despite the low yield, however, several of the 

tested wells showed a good comparison between VOC 

concentrations obtained from the PDB samplers and 

VOC concentrations obtained by using a pump 

(table 3). 

The comparison between the two methods was 

considered acceptable if the concentrations for particular contaminants agreed within 10 μg/L, or within 10 

percent, or the concentration in the PDB sample was 

higher than in the pumped sample. Five of the tested 

wells (wells 1-NEC-15-P, 1-NEC-MW17-S, 1-NEMW23-S, 1-NW-MW24-S, and 1-NW-MW24-P) 

contained detectable contamination and showed a relation between the PDB-sampler results and the pumpedsample results for most compounds, suggesting that 

the PDB samplers accurately reflected ambient 

contaminant concentrations. 

The PDB-sampler concentrations differed from 

the pumped sample concentrations by only 3 μg/L or 

less in well 1-NEC-MW15-P. At well 1-NEC-MW17-S, 

the PDB-sample toluene concentration differed from 

the pumped-sample toluene concentration by only 

3 μg/L, and the PDB-sample benzene concentration 

was slightly higher than the pumped-sample benzene 

concentration (table 4), implying that the PDB sample 

accurately reflected ambient concentrations in the 

adjacent aquifer. 

Table 3. Summary of passive diffusion bag (PDB) sampler results, Naval Surface Warfare Center, Louisville, Kentucky

[VOCs, volatile organic compounds; LNAPL, light non-aqueous phase liquid]

Well

Does PDB 

sampler seem to 

reflect formation 

concentrations?

Comments

1-NEC-MW15-P Yes

1-NE-MW23-P Uncertain Probable redox stratification.

1-NW-MW24-P Yes

1-NEC-MW34-P No Possible explanations include (1) partial exposure of the PDB sampler above the water; 

(2) volatilization losses in the wellbore; (3) discreet-zone contaminant source. Further 

investigation is needed before relying on PDB samplers in this well. 

1-NW-MW6-I Yes No VOCs detected.

1-SE-MW13-I Yes No VOCs detected.

1-NEC-MW15-S Uncertain Good match for most compounds, but poor match for total xylenes. Possible explanations 

include (1) neither conventional nor PDB samplers adequately reflect formation concentrations in this low-yielding well; (2) PDB samplers may not have fully characterized stratification because they only covered 5 feet of the 10-foot well screen; (3) the depths of maximum 

total xylene and maximum total chlorinated solvent concentrations may not coincide. 

1-NEC-MW17-S Yes

1-NE-MW23-S Yes

1-NW-MW24-S Yes

1-NEC-MW34-S Uncertain PDB sampler passed through LNAPL during deployment.
Results and Discussion 7

Table 4. Comparison of volatile organic compound concentrations in passive diffusion bag samples and pumped samples, September 1999 and January 2000, and historical sampling results, Naval Surface Warfare Center, Louisville, Kentucky [μg/L, micrograms per liter; #, data from Tetra Tech NUS, Inc. (2000); PDB, concentrations from passive diffusion bag sampler; pump, concentrations from pumped sample; Comp, 

comparison of PDB and pumped sample. Black cells represent concentrations differences less than 5 μg/L, dark gray cells represent concentration differences less than 10 μg/L, and the 

numbers represent the percentage concentration difference between the diffusion sample and the pumped sample; NS, no sample; <, less than; J, estimated concentration for a parameter detected below the method detection limit; ---, comparison not applicable]

Well

Depth (feet 

below

sea level)

Benzene (μg/L) 2-Butanone (μg/L) Toluene (μg/L)

Historical data# September 1999 January 2000 Historical data# September 1999 January 2000 Historical data# September 1999 January 2000

Sept.

1999

Jan. 

2000 1996 1999 PDB Pump Comp PDB Pump# Comp 1996 1999 PDB Pump Comp Dif Pump# Comp 1996 1999 PDB Pump Comp PDB Pump# Comp

1-NEC-MW15-P 12 NS <330 <5 <5 <5 - - - NS NS - - - <330 <10 <10 <10 - - - NS NS - - - <330 NS <5 <5 - - - NS NS - - -1-NE-MW23-P 9 9 NS <5 5.6 <5 - - - 0.6J <1 - - - NS <10 <10 <10 - - - 5J <5 - - - NS <5 <5 <5 - - - <1 <1 - - -1-NW-MW24-P 11.5 NS NS <5 <5 <5 - - - NS NS - - - NS <10J <10 <10 - - - NS NS - - - NS <5 <5 <5 - - - NS NS - - -1-NEC-MW34-P 8 9 NS <5,000 <5 <5 - - - 2 <1 - - - NS <1,000 <10 <10 - - - <5 <5 - - - NS <5,000 <5 <5 - - - <1 <1 - - -1-NW-MW6-I NS 16 <10 <5 NS NS - - - <1 <1 - - - <10 <10 NS NS - - - 4J <5 - - - <10 <5 NS NS - - - <1 <1 - - -1-SE-MW13-I 21 NS <10 <5 <5 <5 - - - NS NS - - - <10 <10 <10 <10 - - - NS NS - - - <10 <5 <5 <5 - - - NS NS - - -1-NEC-MW15-S 35 34 5J 1.9 <5 <5 - - - 1 3 <10 <10 <10 <10 - - - 6 6 17 6.1 11 11 4 16 75 1-NEC-MW15-S NS 39 NS NS - - - 4 NS NS - - - 5J - - - NS NS - - - 141-NEC-MW17-S 38 NS 2J 36 46 36 NS NS - - - <10 <10 <10 21 - - - NS NS - - - 3J 30 16 13 NS NS - - -1-NE-MW23-S 25 25 NS <5 NS <5 - - - 54 <1 - - - NS <10 NS <10 - - - 9 <5 - - - NS <5 NS <5 - - - 18 <1 - - -1-NE-MW23-S NS 33 NS NS - - - 60 - - - NS NS - - - 9 - - - NS NS - - - 24 - - -1-NE-MW23-S 44 44.6 59 51 61 - - - <10 14 - - - 10 - - - <5 <5 - - - 26 - - -1-NW-MW24-S 25 25.6 NS <100 NS <5 - - - 5 3 NS <200 NS <10 - - - <5 <5 - - - NS 2100 NS 18 - - - 12 24 501-NW-MW24-S 30 30.8 17 14 4 <10 <10 - - - <5 - - - 61 59 86 721-NW-MW24-S NS 37 NS NS - - - 4 NS NS - - - 4J - - - NS NS - - - 70 661-NEC-MW34-S NS 32.9 NS 190 NS NS - - - 160 81 49 NS <330 NS NS - - - 110 54J - - - NS 280 NS NS - - - 28 28
8 Evaluation of Passive Diffusion Bag Samplers in Selected Wells at the Naval Surface Warfare Center, Louisville, Kentucky, 

July 1999 to January 2000 Well Depth (feet below sea level) Ethyl benzene (μg/L) Total xylenes (μg/L) Methyl-tert-butyl ether (μg/L) Historical data# September 1999 January 2000 Historical data# September 1999 January 2000 Historical data# September 1999 January 2000 Sept. 1999 Jan. 2000 1996 1999 PDB Pump Comp PDB Pump# Comp 1996 1999 PDB Pump Comp PDB Pump# Comp 1996 1999 PDB Pump Comp PDB Pump# Comp 1-NEC-MW15-P 12 NS <330 <5 <5 <5 - - - NS NS - - - <330 <5 <5 <5 - - - NS NS - - - - - - NS <5 <5 - - - NS NS - - -

1-NE-MW23-P 9 9 NS <5 <5 <5 - - - <1 <1 - - - NS <5 <5 <5 - - - <1 <1 - - - NS NS <5 <5 - - - <10 <10 - - -1-NW-MW24-P 11.5 NS NS <5 <5 <5 - - - NS NS - - - NS <5 <5 <5 - - - NS NS - - - NS NS <5 <5 - - - NS NS - - -1-NEC-MW34-P 8 9 NS <5,000 <5 <5 - - - <1 <1 - - - NS <5,000 <5 <5 - - - <1 <1 - - - NS NS <5 <5 - - - <10 <10 - - -1-NW-MW6-I NS 16 <10 <5 NS NS - - - <1 <1 - - - <10 <5 NS NS - - - <1 <1 - - - - - - - - - NS NS - - - <10 <10 - - -1-SE-MW13-I 21 NS <10 <5 <5 <5 - - - NS NS - - - <10 <5 <5 <5 - - - NS NS - - - - - - NS <5 <5 - - - NS NS - - -1-NEC-MW15-S 35 34 6J 3.3 <5 7.5 - - - 3 12 75 23 14 6 25 76 11 44 75 - - - NS <5 <5 - - - <10 <10 - - -1-NEC-MW15-S NS 39 NS NS - - - 5 NS NS - - - 17 61 NS NS - - - <10 - - -1-NEC-MW17-S 38 NS <10 11 <5 <5 - - - NS NS - - - 1J 37 <5 <5 - - - NS NS - - - - - - NS <5 <5 - - - NS NS - - -1-NE-MW23-S 25 25 NS <5 NS <5 - - - 17 <1 - - - NS <5 NS <5 - - - 39 <1 - - - NS NS NS <5 - - - <10 <10 - - -1-NE-MW23-S NS 33 NS NS - - - 32 - - - NS NS - - - 82 - - - NS NS - - - <10 - - -1-NE-MW23-S 44 44.6 24 16 38 - - - 48 34 29 110 - - - <5 <5 - - - <10 - - -1-NW-MW24-S 25 25.6 NS <100 NS 96 - - - 36 150 76 NS 5200 NS 350 - - - 180 680 74 NS NS NS 29 - - - <10 5J - - -1-NW-MW24-S 30 30.8 410 220 46 270 44 1900 1100 42 1300 48 53 31 42 <10 - - -1-NW-MW24-S NS 37 NS NS - - - 200 25 NS NS - - - 960 29 NS NS - - - <10 - - -1-NEC-MW34-S NS 32.9 NS 90J NS NS - - - 82 68 17 NS 320 NS NS - - - 180 140 22 NS - - - NS NS - - - <10 <10 - - -

Table 4. Comparison of volatile organic compound concentrations in passive diffusion bag samples and pumped samples, September 1999 and January 2000, and historical sampling results, Naval Surface Warfare Center, Louisville, Kentucky (Continued)[μg/L, micrograms per liter; #, data from Tetra Tech NUS, Inc. (2000); PDB, concentrations from passive diffusion bag sampler; pump, concentrations from pumped sample; Comp, 

comparison of PDB and pumped sample. Black cells represent concentrations differences less than 5 μg/L, dark gray cells represent concentration differences less than 10 μg/L, and the 

numbers represent the percentage concentration difference between the diffusion sample and the pumped sample; NS, no sample; <, less than; J, estimated concentration for a parameter detected below the method detection limit; ---, comparison not applicable]
Results and Discussion 9

Well

Depth (feet 

below

sea level)

Naphthalene (μg/L) Styrene (μg/L) Tetrachloroethene (μg/L)

Historical data# September 1999 January 2000 Historical data# September 1999 January 2000 Historical data# September 1999 January 2000

Sept.

1999

Jan. 

2000 1996 1999 PDB Pump Comp PDB Pump# Comp 1996 1999 PDB Pump Comp PDB Pump# Comp 1996 1999 PDB Pump Comp PDB Pump# Comp

1-NEC-MW15-P 12 NS <10 <10 <5 <5 - - - NS NS - - - <330 <5 <5 <5 - - - NS NS - - - <330 <5 <5 <5 - - - NS NS - - -1-NE-MW23-P 9 9 NS <10 <5 <5 - - - - - - <10 - - - NS <5 <5 <5 - - - <1 <1 - - - NS 16 19 57 67 30 19 371-NW-MW24-P 11.5 NS NS <10 <5 <5 - - - NS NS - - - NS <5 <5 <5 - - - NS NS - - - NS 69 58 19 67 NS NS - - -1-NEC-MW34-P 8 9 NS <10 <5 <5 - - - - - - <10 - - - NS <5,000 <5 <5 - - - <1 <1 - - - NS <5,000 <5 <5 - - - <1 <1 - - -1-NW-MW6-I NS 16 <10 <10 NS NS - - - - - - <11 - - - <10 <5 NS NS - - - <1 <1 - - - <10 <5 NS NS - - - <1 <1 - - -1-SE-MW13-I 21 NS <10 <10 <5 <5 - - - NS NS - - - <10 <5 <5 <5 - - - NS NS - - - <10 <5 <5 <5 - - - NS NS - - -1-NEC-MW15-S 35 34 2J <10 <5 <5 - - - - - - <10 - - - <10 <5 <5 <5 - - - <1 <1 - - - <10 <5 <5 <5 - - - <1 <1 - - -1-NEC-MW15-S NS 39 NS NS - - - - - - - - - NS NS - - - <1 - - - NS NS - - - <1 - - -1-NEC-MW17-S 38 NS - - - <10 <5 <5 - - - NS NS - - - <10 <5 <5 <5 - - - NS NS - - - <10 <5 <5 <5 - - - NS NS - - -1-NE-MW23-S 25 25 NS <13 NS <5 - - - - - - <10 - - - NS <5 <5 <5 - - - <1 <1 - - - NS <5 NS <5 - - - <1 <1 - - -1-NE-MW23-S NS 33 NS NS - - - - - - - - - NS NS - - - <1 - - - NS NS - - - <1 - - -1-NE-MW23-S 44 44.6 <5 <5 - - - - - - - - - <5 <5 - - - <1 - - - <5 <5 - - - <1 - - -1-NW-MW24-S 25 25.6 NS 9.2J NS NS - - - - - - 33 - - - NS <100 NS <5 - - - <1 <1 - - - NS <5 NS <5 - - - <1 <1 - - -1-NW-MW24-S 30 30.8 70 69 - - - - - - 17 12 <1 - - - <5 <5 - - - <1 - - -1-NW-MW24-S NS 37 NS NS - - - - - - - - - NS NS - - - <1 - - - NS NS - - - <1 - - -1-NEC-MW34-S NS 32.9 NS 180J NS NS - - - - - - 7J - - - NS <170 NS NS - - - <1 <1 - - - NS <170 NS NS - - - <1 <1 - - -

Table 4. Comparison of volatile organic compound concentrations in passive diffusion bag samples and pumped samples, September 1999 and January 2000, and historical sampling results, Naval Surface Warfare Center, Louisville, Kentucky (Continued)[μg/L, micrograms per liter; #, data from Tetra Tech NUS, Inc. (2000); PDB, concentrations from passive diffusion bag sampler; pump, concentrations from pumped sample; Comp, 

comparison of PDB and pumped sample. Black cells represent concentrations differences less than 5 μg/L, dark gray cells represent concentration differences less than 10 μg/L, and the 

numbers represent the percentage concentration difference between the diffusion sample and the pumped sample; NS, no sample; <, less than; J, estimated concentration for a parameter detected below the method detection limit; ---, comparison not applicable]
10 Evaluation of Passive Diffusion Bag Samplers in Selected Wells at the Naval Surface Warfare Center, Louisville, Kentucky, 

July 1999 to January 2000 Well Depth (feet below sea level) Methylene chloride (μg/L) cis-1,2-Dichloroethene (μg/L) trans-1,2-Dichloroethene (μg/L) Historical data# September 1999 January 2000 Historical data# September 1999 January 2000 Historical data# September 1999 January 2000 Sept. 1999 Jan. 2000 1996 1999 PDB Pump Comp PDB Pump# Comp 1996 1999 PDB Pump Comp PDB Pump# Comp 1996 1999 PDB Pump Comp PDB Pump# Comp 1-NEC-MW15-P 12 NS <330 2.5J <5 <5 - - - NS NS - - - - - - 8.2 5.1 6.1 NS NS - - - - - - <5 <5 <5 - - - NS NS - - -

1-NE-MW23-P 9 9 NS 18 <5 <5 - - - <1 <1 - - - NS 16 240 210 13 110 62 44 NS <5 14 10 4 21-NW-MW24-P 11.5 NS NS 69 <5 <5 - - - NS NS - - - NS <5 <5 <5 - - - NS NS - - - NS <5 <5 <5 - - - NS NS - - -1-NEC-MW34-P 8 9 NS <5,000 <5 <250 - - - 0.5JB <1 - - - NS 12,000 1,300 6,500 80 3,200 28,000 89 NS <5,000 64 100 36 39 130 701-NW-MW6-I NS 16 <10 <5 NS NS - - - 0.6JB <1 - - - - - - <5 NS NS - - - <2 <2 - - - - - - <5 NS NS - - - <2 <2 - - -1-SE-MW13-I 21 NS <10 <5 <5 <5 - - - NS NS - - - <10 <5 <5 <5 - - - NS NS - - - - - - <5 <5 <5 - - - NS NS - - -1-NEC-MW15-S 35 34 <10 <5 <5 <5 - - - <1 <1 - - - - - - <5 <5 <5 - - - <2 <2 - - - - - - <5 <5 <5 - - - <2 <2 - - -1-NEC-MW15-S NS 39 NS NS - - - <1 - - - NS NS - - - <2 - - - NS NS - - - <2 - - -1-NEC-MW17-S 38 NS <10 <5 <5 <5 - - - NS NS - - - - - - <5 <5 <5 - - - NS NS - - - - - - <5 <5 <5 - - - NS NS - - -1-NE-MW23-S 25 25 NS <5 NS <5 - - - 1B <1 - - - NS <5 NS <5 - - - 2J <2 - - - NS <5 NS <5 - - - <2 <2 - - -1-NE-MW23-S NS 33 NS NS - - - <1 - - - NS NS - - - 1J - - - NS NS - - - <2 - - -1-NE-MW23-S 44 44.6 9.6 7.5 <1 - - - <5 <5 - - - 1J - - - <5 <5 - - - <2 - - -1-NW-MW24-S 25 25.6 NS <100 NS NS - - - 0.5JB <1 - - - NS <100 NS NS - - - <2 <2 - - - NS <100 NS NS - - - <2 <2 - - -1-NW-MW24-S 30 30.8 <5 <5 - - - 2B - - - <5 <5 - - - <2 - - - <5 <5 - - - <2 - - -1-NW-MW24-S NS 37 NS NS - - - 0.7JB - - - NS NS - - - <2 - - - NS NS - - - <2 - - -1-NEC-MW34-S NS 32.9 NS <170 NS NS - - - <1 <1 - - - NS <170 NS NS - - - <2 <2 - - - NS <170 NS NS - - - <2 <2 - - -

Table 4. Comparison of volatile organic compound concentrations in passive diffusion bag samples and pumped samples, September 1999 and January 2000, and historical sampling results, Naval Surface Warfare Center, Louisville, Kentucky (Continued)[μg/L, micrograms per liter; #, data from Tetra Tech NUS, Inc. (2000); PDB, concentrations from passive diffusion bag sampler; pump, concentrations from pumped sample; Comp, 

comparison of PDB and pumped sample. Black cells represent concentrations differences less than 5 μg/L, dark gray cells represent concentration differences less than 10 μg/L, and the 

numbers represent the percentage concentration difference between the diffusion sample and the pumped sample; NS, no sample; <, less than; J, estimated concentration for a parameter detected below the method detection limit; ---, comparison not applicable]
Results and Discussion 11

Well

Depth (feet 

below

sea level)

Trichloroethene (μg/L) Vinyl chloride (μg/L) Chloroethane (μg/L)

Historical data# September 1999 January 2000 Historical data# September 1999 January 2000 Historical data# September 1999 January 2000

Sept.

1999

Jan. 

2000 1996 1999 PDB Pump Comp PDB Pump# Comp 1996 1999 PDB Pump Comp PDB Pump# Comp 1996 1999 PDB Pump Comp PDB Pump# Comp

1-NEC-MW15-P 12 NS 2,000 34 47 50 NS NS - - - 54J 6.6 <2 <2 - - - NS NS - - - <330 <5 <5 <5 - - - NS NS - - -1-NE-MW23-P 9 9 NS 5.9 68 110 38 34 16 53 NS 1.3J 5.3 26 80 <2 7 - - - NS <5 <5 <5 - - - <2 <2 - - -1-NW-MW24-P 11.5 NS NS 17 9.3 8.3 NS NS - - - NS <5 <2 <2 - - - NS NS - - - NS <5 <5 <5 - - - NS NS - - -1-NEC-MW34-P 8 9 NS <5,000 14 76 82 12 310 96 NS <5,000 120 510 76 87 890 90 NS <5,000 5.2 <250 - - - <2 <2 - - -1-NW-MW6-I NS 16 <10 <5 NS NS - - - <1 <1 - - - <2 <5 NS NS - - - <2 <2 - - - <10 <5 NS NS - - - <2 <2 - - -1-SE-MW13-I 21 NS <10 <5 <5 <5 - - - NS NS - - - <2 <5 <2 <2 - - - NS NS - - - <10 <5 <5 <5 - - - NS NS - - -1-NEC-MW15-S 35 34 <10 <5 <5 <5 - - - <1 <1 - - - <2 <5 <2 <2 - - - 1J <2 - - - <10 <5 <5 <5 - - - <2 <2 - - -1-NEC-MW15-S NS 39 NS NS - - - <1 - - - NS NS - - - <2 - - - NS NS - - - <2 - - -1-NEC-MW17-S 38 NS <10 <5 <5 <5 - - - NS NS - - - <2 <5 <2 <2 - - - NS NS - - - <10 <5 <5 <5 - - - NS NS - - -1-NE-MW23-S 25 25 NS <5 NS <5 - - - <1 <1 - - - NS <5 NS <2 - - - <2 <2 - - - NS <5 NS <5 - - - <2 <2 - - -1-NE-MW23-S NS 33 NS NS - - - <1 - - - NS NS - - - <2 - - - NS NS - - - <2 - - -1-NE-MW23-S 44 44.6 <5 <5 - - - <1 - - - <2 <2 - - - <2 - - - <5 <5 - - - <2 - - -1-NW-MW24-S 25 25.6 NS <100 NS NS - - - <1 <1 - - - NS <100 NS NS - - - <2 <2 - - - NS 1 NS NS - - - <2 <2 - - -1-NW-MW24-S 30 30.8 <5 <5 - - - <1 - - - <2 <2 - - - <2 - - - <5 <5 - - - <2 - - -1-NW-MW24-S NS 37 NS NS - - - <1 - - - NS NS - - - <2 - - - NS NS - - - <2 - - -1-NEC-MW34-S NS 32.9 NS <170 NS NS - - - <1 <1 - - - NS <170 NS NS - - - <2 <2 - - - NS <170 NS NS - - - <2 <2 - - -

Table 4. Comparison of volatile organic compound concentrations in passive diffusion bag samples and pumped samples, September 1999 and January 2000, and historical sampling results, Naval Surface Warfare Center, Louisville, Kentucky (Continued)[μg/L, micrograms per liter; #, data from Tetra Tech NUS, Inc. (2000); PDB, concentrations from passive diffusion bag sampler; pump, concentrations from pumped sample; Comp, 

comparison of PDB and pumped sample. Black cells represent concentrations differences less than 5 μg/L, dark gray cells represent concentration differences less than 10 μg/L, and the 

numbers represent the percentage concentration difference between the diffusion sample and the pumped sample; NS, no sample; <, less than; J, estimated concentration for a parameter detected below the method detection limit; ---, comparison not applicable]
12 Evaluation of Passive Diffusion Bag Samplers in Selected Wells at the Naval Surface Warfare Center, Louisville, Kentucky, 

July 1999 to January 2000

Benzene, in micrograms per liter

0 5 10 15 20 25 30

Depth, in feet below top of casing

20

25

30

35

40

Toluene and ethyl benzene, in micrograms per liter

0 100 200 300 400

Total xylenes, in micrograms per liter

0 500 1000 1500

Benzene in PDB sampler

Toluene in PDB sampler

Ethyl benzene in PDB sampler

Total xylenes in PDB sampler

Benzene in pumped sample

Toluene in pumped sample

Ethyl benzene in pumped sample

Total xylenes in pumped sample

The PDB sampler slightly underestimated the 

2-butanone concentration in ground water at well 

1-NEC-MW17-S, but this does not seem to be an 

inability of the PDB sampler to quantify that compound because a close match between PDB-sample 

and pumped-sample 2-butanone concentrations was 

obtained at well 1-NE-MW23-S (table 4). The data 

suggest that the use of PDB samplers provide a viable 

alternative to collecting pumped samples in these 

wells. 

The PDB-sampler data from well 1-NW-MW24-S 

(table 4) seem to be more representative of formation 

water than the pumped-sample data, despite the relatively large concentration differences between methods. The PDB-sampler data strongly suggest that 

contaminant stratification is present in the screened 

interval of the well (fig. 2). Although the VOC concentrations from the pumped sample and the adjacent 

PDB sample differ substantially in ground water from 

well 1-NW-MW24-S, the pumped-sample results for 

Figure 2. Comparison of benzene, toluene, ethyl benzene, and total 

xylenes concentrations in passive diffusion bag (PDB) samplers and in 

pumped samples, well 1-NW-MW24-S, Naval Surface Warfare Center, 

Louisville, Kentucky, January 2000.
Results and Discussion 13

most compounds are within the range found by using 

the PDB samplers. The data suggest that the PDB 

samplers in well 1-NW-MW24-S reveal the contaminant stratification, and the pumped sample produces a 

mixed sample that incorporates water from both the 

lightly contaminated and heavily contaminated horizons (fig. 2). Moreover, although methyl-tert-butyl 

ether (MTBE) is not a compound recommended for use 

with PDB samplers because of the potential to underestimate actual concentrations (Vroblesky, 2001), the 

PDB samples from well 1-NW-MW24-S contained 

higher MTBE concentrations than the pumped sample. 

These data suggest that the PDB samplers provided a 

more accurate MTBE sample than the pumped sample. 

Thus, PDB samplers seem to be a viable alternative to 

collecting pumped samples in this well. 

At well 1-NE-MW23-S, the two sampling 

methods did not agree; the PDB sampler produced 

higher VOC concentrations, suggesting that the PDB 

sampler more accurately revealed the higher concentrations than the pumped sample. In well 1-NE-MW23-S, 

the January 2000 pumped-sample data show no detectable contaminant concentrations. The PDB-sample 

data, however, show stratified contamination (table 4), 

with the lowest concentrations in the upper vuggy 

limestone and the highest concentrations near the 

bottom of the screened interval. Because well 1-NEMW23-S contained a 20-ft saturated screened interval 

(table 2), it is highly probable that the screen transects 

zones of differing contaminant concentration. Thus, the 

PDB data from this well seem to more precisely define 

the contaminant concentrations than the pumped 

samples, which probably represent uncontaminated 

water or a mixture of contaminated and uncontaminated water with resulting low or undetectable VOC 

concentrations. 

Well 1-NW-MW24-P also is a well in which the 

two methods did not agree; the PDB sampler produced 

higher VOC concentrations than the pumped sample. 

Unlike well 1-NE-MW23-S, well 1-NW-MW24-P 

contained only about 1 ft of saturated screened interval. 

The small saturated interval suggests the possibility 

that the PDB samplers may have been partly out of the 

water column. Further concern regarding the PDB 

sampler is that the aquifer at the well is low yielding. 

Pumping the well to collect samples essentially dried 

up the well, and only 2 in. of water were in the well by 

the next day, indicating poor recovery. Despite this, the 

fact that the PDB sampler produced higher VOC 

concentrations than the pumped sample implies that the 

PDB sampler produced more representative concentrations. The low aquifer permeability and the potential 

for partial exposure of the PDB samplers to unsaturated conditions suggests the possibility that both 

sampling methods underestimated actual local VOC 

concentrations, but that the PDB sampler produced 

more realistic concentrations than the pumped sample 

in this well. 

Well 1-NEC-MW34-S is another well in which 

the results of the two methods did not agree for most 

detected compounds, and the PDB sampler produced 

the higher concentrations (table 4). In this case, however, there is some uncertainty in the results because 

the sample was lowered through a layer of LNAPL. 

The effect of such a layer has not been thoroughly 

tested, and carryover from product sorbed to the polyethylene may have artificially produced higher than 

local concentrations in the PDB sampler. Future PDB 

tests in this well could be performed more confidently 

by using a method described in Vroblesky and Peters 

(2000) in which a capped pipe is lowered through the 

product, the cap is then removed with a rod and recovered by means of a line attached to the cap outside of 

the pipe; the PDB samplers then are lowered through 

the pipe past the product and into the well.

Despite the poor yield of the aquifer at well 

1-NEC-MW15-S, the analytical data showed a good 

match at one or more depths between sampling methodologies for all detected contaminants (benzene, 

2-butanone, toluene, and ethyl benzene) except total 

xylenes (table 4). Total xylenes concentrations differed 

by up to 76 percent, with the PDB samplers underestimating the concentrations. The reason for this 

difference, even though all of the other compounds 

closely match, is not clear. One concern is that well 

1-NEC-MW15-S is screened in a poorly permeable 

zone. In September 1999, after pumping the well 

slowly (78 mL/min) for 1 hour and 42 minutes, the 

water level in the well continued to draw down, indicating that the pumped water probably was derived 

from storage in the well rather than from the aquifer. 

The poor exchange of water between the aquifer and 

the well screen may account for the difference in total 

xylenes concentrations between the two methods. 

However, even the pumped sample may not be representative of the aquifer concentrations because of poor 

yield. Alternatively, because the diffusion samplers 

were spread out over only 5 ft of the 10-ft saturated 

well screen (table 2), the PDB samplers may not have 

fully characterized the stratification. Higher total 
14 Evaluation of Passive Diffusion Bag Samplers in Selected Wells at the Naval Surface Warfare Center, Louisville, Kentucky, 

July 1999 to January 2000

xylenes concentrations may be present at depths within 

the screened interval other than the PDB-samplertested depths. Thus, although the data imply that the 

use of PDB samplers in well 1-NEC-MW15-S can 

provide benzene, 2-butanone, toluene, and ethyl benzene 

concentrations similar to those obtained by pumping, 

questions remain regarding confident quantification of 

total xylenes and whether even the pumped sample is 

representative of formation concentrations.

A second well, 1-NE-MW23-P, showed mixed 

or ambiguous test results when PDB-sampler results 

were compared to pumped-sample results. The results 

from the September 1999 and January 2000 sampling 

events showed a close trans-1,2 dichloroethene concentration match between the methods (the differences 

between the methods ranged from 2 to 4 μg/L); however, the concentration difference between the remaining detected compounds ranged from 13 to 80 percent. 

The PDB sampler provided higher concentrations than 

the pumped sample for some of the detected compounds (benzene, cis-1,2-dichloroethene, and trans1,2-dichloroethene) during the first sampling and for 

all of the detected compounds except vinyl chloride 

during the second sampling. The uncertainty in deciding whether the PDB sampler provided a viable alternative sampling method in this well lies in the fact 

that the pumped sample collected higher concentrations of tetrachloroethene (67 percent), trichloroethene 

(38 percent), and vinyl chloride (80 percent) than the 

PDB sampler during the September 1999 sampling. 

A possible explanation for the differences 

between the methods at well 1-NE-MW23-P lies in the 

probability of chemical stratification in the screened 

interval. Although there was only about 4.89 to 5 ft of 

saturated interval in this well during sampling (table 2), 

sampling observations indicate the presence of a sharp 

chemical gradient. During the September 1999 sampling, after purging only 2 gal of water from the bottom 

of the well, the discharging water contained only a low 

amount of dissolved oxygen [0.7 millgrams per liter 

(mg/L)]; however, after purging 4 gal, the discharging 

water contained substantially more dissolved oxygen 

(2.5 mg/L). These results suggest that there is a thin 

zone of anaerobic water near the base of the screened 

interval and an oxygenated zone near the top of the 

screened interval that became increasingly mixed during pumping. Support for this hypothesis is the observation that the bottom part of the rope connected to the 

PDB sampler was stained black, suggesting deposition 

of reduced sulfur or iron species in an anaerobic 

environment (dissolved oxygen data and physical 

observations are not available for the January 2000 

sampling). The presence of redox stratification, as suggested here, may also indicate chlorinated solvent stratification. If such stratification is present and is of a finer 

scale then the length of the PDB sampler, then the VOC 

concentrations in the PDB sampler also may be stratified, resulting in a mixed concentration within the sampler and possibly producing results that underestimate 

concentrations in the small stratified zone. In addition, 

the concentrations in the pumped sample may vary 

depending on the position of the pump inlet relative to 

the stratification and the length of pumping time prior to 

sample collection. If a pumped sample is used to obtain 

these data, then care should be taken to pump a consistent volume of water prior to sampling to increase the 

comparability of data among sampling events.

In one well (1-NEC-MW34-P), the PDB sampler 

provided a poor comparison to the pumped sample. 

Although benzene concentrations showed a close match 

between sampling methods, the concentrations of most 

of the remaining detected compounds were substantially lower in the PDB sampler (by 36-96 percent) 

than in the pumped sample. 

Three possible explanations can be postulated 

for the difference. (1) The PDB sampler may have 

been partially exposed above the water table prior to 

the sampling events because there was only 2.65 to 

2.83 ft of saturated screened interval during the sampling events (table 2). (2) Because of the small saturated interval, the rate of volatilization loss in the 

wellbore may have exceeded the rate of VOC exchange 

with the aquifer, resulting in concentrations in the 

wellbore not representative of the aquifer. (3) It is 

possible that the contributing zone of contaminant was 

small relative to the size of the diffusion sampler, in 

which case the PDB sampler may have averaged concentrations, whereas much of the water sampled by the 

pump may have been derived directly from the contributing zone. For well 1-NEC-MW34-P, the simplest 

resolution is to continue sampling the well by purging. 

Alternatively, if the use of a PDB sampler is desired, 

then further testing at the well should be done with a 

shorter PDB sampler. 

In the wells where multiple PDB samplers were 

used to evaluate the vuggy limestone (wells 1-NECMW15-S and 1-NW-MW24-S), the PDB-sampler data 

supported the findings from colloidal borescope data, 

indicating that the vuggy limestone was not a zone that 

supplied water to the wells (Aqua VISION, 1999). 
Summary 15

The PDB-sampler data showed lower VOC concentrations adjacent to the vuggy limestone and higher VOC 

concentrations deeper in the limestone.

Analysis of the ground-water sampling data 

show that both the PDB samplers and the pumped 

samples from 2 of the 11 tested wells (wells 1-NWMW6-I and 1-SE-MW13-I) contained no detectable 

contaminant concentrations except for estimated 

concentrations (J values) (table 4) below the detection 

limit of methylene chloride and 2-butanone in the PDB 

sample from well 1-NW-MW6-I. 

SUMMARY 

PDB samplers were tested in 11 wells at NSWC 

Louisville, Ky., by comparing the VOC concentrations 

obtained from PDB samplers to VOC concentrations 

obtained by pumping the wells. Despite the poorly 

permeable nature of the fractured-rock aquifer at the 

site, several of the tested wells showed a good comparison between VOC concentrations obtained from the 

PDB samplers and VOC concentrations obtained by 

using a pump. The comparison between the PDB 

sampler and the pumped sample was considered 

acceptable if the concentrations for particular contaminants agreed within 10 μg/L, or within 10 percent, or 

the concentration in the PDB sample was higher than in 

the pumped sample. Five of the tested wells (wells 

1-NEC-MW15-P, 1-NEC-MW17-S, 1-NE-MW23-S, 

1-NW-MW24-S, and 1-NW-MW24-P) contained 

detectable contamination and showed a relation between 

the PDB-sampler results and the pumped-sample 

results suggesting that the PDB-samplers accurately 

reflected ambient contaminant concentrations. 

In two wells where the data suggest that the 

PDB samplers produced the more representative 

results (wells 1-NE-MW23-S and 1-NW-MW24-P), 

VOC concentrations from the two methods did not 

agree; the PDB sampler produced the higher concentrations. The concentration differences in well 1-NWMW23-S probably are attributable to low values resulting from mixing of stratified waters during pumping. 

In well 1-NW-MW24-P, the PDB sampler produced 

higher concentrations than the pumped sample despite 

a short saturated interval (about 1 ft) and a low-yielding aquifer. The PDB sampler and the pumped sample 

both may have underestimated actual concentrations, 

but the data suggest that the PDB sampler produced 

more realistic concentrations than the pumped sample 

in this well. In a third well where the PDB sampler 

produced higher concentrations than the pumped 

sample (well 1-NEC-MW34-S), it is unclear whether 

the PDB sampler produced the more representative 

results or whether the higher concentrations in the 

PDB sampler were the result of carryover after having 

passed through a layer of light non-aqueous-phase 

liquid during deployment. 

The data from well 1-NEC-MW15-S showed a 

good match between sampling methodologies for all 

detected contaminants (benzene, 2-butanone, toluene, 

and ethyl benzene), but a poor match for total xylenes. 

It is unclear why the xylene concentrations differed 

substantially whereas concentrations of all the other 

compounds closely matched. Explanations include the 

possibility that neither method adequately represents 

ambient conditions in this well because of poor 

exchange of water between the aquifer and the well 

screen in this low-yielding well. Alternatively, the 

PDB samplers may not have fully characterized the 

stratification because the diffusion samplers were 

spread out over only 5 ft of the 10-ft saturated well 

screen. Higher total xylenes concentrations may be 

present at depths within the screened interval other 

than the PDB-sampler-tested depths or in an area not 

adjacent to the screened interval and transported to the 

well by pumping during well purging and sampling. 

Thus, although the data imply that the use of PDB 

samplers in well 1-NEC-MW15-S can provide benzene, 2-butanone, toluene, and ethyl benzene concentrations similar to those obtained by pumping, questions 

remain regarding confident quantification of total 

xylenes and whether even the pumped sample is 

representative of formation concentrations.

Similarly, well 1-NE-MW23-P showed a close 

match between the two methods for trans-1,2 dichloroethene concentrations in September 1999 and January 

2000; however, there were differences between the 

methods for other detected compounds. Geochemical 

evidence indicates the presence of redox stratification 

in the saturated interval of this well, which may also 

indicate chlorinated solvent stratification. If so, then 

the VOC concentrations in the PDB sampler represent 

an average over the length of the sampler, and the concentrations in the pumped sample may vary depending 

on the depth of the pump and the length of pumping 

time prior to sample collection. Under these conditions, the use of a PDB sampler at a specific target 

horizon may provide concentrations representative of 

local conditions. If a pumped sample is used to obtain 

these data, then care should be taken to pump a consistent volume of water prior to sampling to increase the 

comparability of data among sampling events.
16 Evaluation of Passive Diffusion Bag Samplers in Selected Wells at the Naval Surface Warfare Center, Louisville, Kentucky, 

July 1999 to January 2000

In one well (1-NEC-MW34-P), the PDB 

sampler provided a poor comparison to the pumped 

sample. Possible explanations include partial exposure 

of the sampler above the water table, volatilization loss 

from the wellbore at a rate faster than the exchange with 

the aquifer, or contaminant inflow to the well through 

a smaller zone than the length of the sampler, resulting 

in an underestimate of actual concentrations. For well 

1-NEC-MW34-P, the simplest resolution is to continue sampling the well by purging. Alternatively, if 

use of a PDB sampler is desired, then further testing at 

the well should be done with a shorter PDB sampler. 

In the wells where multiple PDB samplers were 

used to evaluate the vuggy limestone (wells 1-NECMW15-S and 1-NW-MW24-S), the PDB-sampler data 

supported the findings from colloidal borescope data 

indicating that the vuggy limestone was not a zone that 

supplied water to the wells. The PDB-sampler data 

showed the lowest VOC concentrations adjacent to the 

vuggy limestone and higher VOC concentrations 

deeper in the limestone.

Analysis of the ground-water sampling data 

show that both the PDB samplers and the pumped 

samples from 2 of the 11 tested wells (wells 1-NWMW6-I and 1-SE-MW13-I) contained no detectable 

contaminant concentrations except for low concentrations of methylene chloride and 2-butanone in the 

PDB sample from well 1-NW-MW6-I. 

REFERENCES 

Aqua VISION, 1999, Colloidal borescope investigation at 

the Naval Ordnance Station, Crane Division, Naval 

Surface Warfare Center (NSWC), Louisville, Kentucky: 

Consultant’s report to Southern Division Naval Facilities Engineering Command, May 19, 1999, 12 p.

Environmental Liability Management, Inc., 1999, Hydrocarbon 

characterization, Naval Ordnance Station, Louisville, Kentucky: Letter report to Dave Olson, TetraTech NUS, Inc, 

Gaithersburg, Md, June 19, 1999, 3 p.

Tetra Tech NUS, Inc., 2000, RCRA Facility Investigation 

Volume 1, Book 2, Naval Ordnance Station Crane 

Division, Naval Surface Warfare Center, Louisville, 

Kentucky: Consultant’s report to Southern Division 

Naval Facilities Engineering Command, September 

2000, 176 p.

U.S. Environmental Protection Agency, 1999, On-line 

SW-846 methods: Accessed December 21, 1999, at 

URL www.epa.gov/epaoswer/hazwaste/test/

tx8xxx.htm#8XXX.

Vroblesky, D.A., 2001, User’s guide for polyethylene-based 

passive diffusion bag samplers to obtain volatile 

organic compound concentrations in wells: Part 1: 

Assembly and quality control and assurance: U.S. Geological Survey Water-Resources Investigations Report 

01-4060, 18 p.

Vroblesky, D.A., and Hyde, W.T., 1997, Diffusion samplers 

as an inexpensive approach to monitoring VOCs in 

ground water: Ground Water Monitoring and Remediation, v. 17, no. 3, p. 177-184. 

Vroblesky, D.A., and Peters, B.C., 2000, Diffusion sampler 

testing at Naval Air Station North Island, San Diego 

County, California, November 1999 to January 2000: 

U.S. Geological Survey Water-Resources Investigations 

Report 00-4182, 27 p.
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