v

CONTENTS

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

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

Purpose and scope .........................................................................................................................................................2

Description of study area...............................................................................................................................................2

Hydrogeologic setting....................................................................................................................................................4

Site history.....................................................................................................................................................................5

Description of contaminant plumes and potential source areas ....................................................................................5

Previous investigations ..................................................................................................................................................9

Acknowledgments .......................................................................................................................................................10

Methods of investigation......................................................................................................................................................10

Changes in ground-water quality between 1995 and 2000–2001 ........................................................................................11

Comparison of maximum concentrations....................................................................................................................11

Distribution of volatile organic compounds ................................................................................................................11

Section A–A′′......................................................................................................................................................11

Total volatile organic compounds (VOCs).................................................................................................11

1,1,2,2–Tetrachloroethane (TeCA).............................................................................................................16

Trichloroethene (TCE) ...............................................................................................................................16

Carbon tetrachloride (CT) ..........................................................................................................................16

Chloroform (CF).........................................................................................................................................16

Section C–C ′ ......................................................................................................................................................17

Total volatile organic compounds (VOCs).................................................................................................17

1,1,2,2–Tetrachloroethane (TeCA).............................................................................................................30

Trichloroethene (TCE) ...............................................................................................................................32

Carbon tetrachloride (CT) ..........................................................................................................................34

Chloroform (CF).........................................................................................................................................36

Summary and conclusions....................................................................................................................................................38

References cited ...................................................................................................................................................................38

Appendix: Sampling locations for wells and piezometers in the West Branch Canal Creek study area,

 Aberdeen Proving Ground, Maryland ...........................................................................................................40

Figures

1–2. Maps showing:

1. Location of the West Branch Canal Creek study area, Aberdeen Proving Ground, Maryland,

and hydrogeologic section X–X ′ ...........................................................................................................2

2. Location of sampling sites and sections A–A′′ and C–C ′ in the wetland study area along

West Branch Canal Creek.......................................................................................................................3

3. Generalized hydrogeologic section X–X′ showing directions of ground-water flow in the Canal Creek area....4

4. Section A–A′′ showing the hydrogeology and locations of piezometer nests and screen depths ........................6

5. Section C–C ′ showing the hydrogeology and locations of piezometer nests and screen depths.........................7

6. Section A–A′′ showing head distribution and generalized ground-water-flow directions at high tide,

December 3, 2001.............................................................................................................................................8

7. Graphs showing chemical differences between contaminant plumes 1 and 2 in 1995 and 2000

in piezometers WB32B (C–C ′ transect) and WB28F (A–A′′ transect), Canal Creek aquifer........................9

8. Graphs showing changes in maximum volatile organic compound concentrations in sections A–A′′

and C–C ′ between 1995 and 2000.................................................................................................................12
vi

Figures—Continued

 9. Distribution of total volatile organic compounds in ground water in section A–A′′:

(a) June–October 1995 .................................................................................................................................13

(b) 2000–2001 ..............................................................................................................................................14

(c) Areas along section A–A′′ where total volatile organic compound concentrations in

ground water increased or decreased between 1995 and 2000 ..........................................................15

10. Distribution of 1,1,2,2–tetrachloroethane (TeCA) in ground water in section A–A′′:

(a) June–October 1995 .................................................................................................................................18

(b) 2000–2001 ..............................................................................................................................................19

11. Distribution of trichloroethene (TCE) in ground water in section A–A′′:

(a) June–October 1995 .................................................................................................................................20

(b) 2000–2001 ..............................................................................................................................................21

12. Distribution of carbon tetrachloride (CT) in ground water in section A–A′′:

(a) June–October 1995 .................................................................................................................................22

(b) 2000–2001 ..............................................................................................................................................23

13. Distribution of chloroform (CF) in ground water in section A–A′′:

(a) June–October 1995 .................................................................................................................................24

(b) 2000–2001 ..............................................................................................................................................25

14. Graphs showing comparison of molar concentrations of carbon tetrachloride (CT) to chloroform (CF) in:

(a) Ground water, 2000–2001 ......................................................................................................................26

(b) Surface water, 1999–2000 ......................................................................................................................26

15. Distribution of total volatile organic compounds in ground water in section C–C ′:

(a) June–October 1995 .................................................................................................................................27

(b) June–August 2000 ..................................................................................................................................28

(c) Areas along section C–C ′ where total volatile organic compound concentrations in

ground water increased or decreased between 1995 and 2000 ..........................................................29

16. Distribution of 1,1,2,2–tetrachloroethane (TeCA) in ground water in section C–C ′:

(a) June–October 1995 .................................................................................................................................30

(b) June–August 2000 ..................................................................................................................................31

17. Distribution of trichloroethene (TCE) in ground water in section C–C ′:

(a) June–October 1995 .................................................................................................................................32

(b) June–August 2000 ..................................................................................................................................33

18. Distribution of carbon tetrachloride (CT) in ground water in section C–C ′:

(a) June–October 1995 .................................................................................................................................34

(b) June–August 2000 ..................................................................................................................................35

19. Distribution of chloroform (CF) in ground water in section C–C ′:

(a) June–October 1995 .................................................................................................................................36

(b) June–August 2000 ..................................................................................................................................37
vii

Conversion Factors and Vertical Datum

_____________________________________________________________________________________________________________________________________

Multiply By To obtain

_____________________________________________________________________________________________________________________________________

inch (in.) 2.54 centimeter

foot (ft) 0.3048 meter

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

gallon (gal) 3.785 liter

_____________________________________________________________________________________________________________________________________

Vertical datum: In this report, “sea level” refers to the National Geodetic Vertical Datum 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.

Other abbreviated units of measure: Water temperature, chemical concentration, and other chemical and physical 

properties of constituents are given in metric units. Water temperature in degrees Celsius (°

C) can be converted to degrees 

Fahrenheit (°

F) by use of the following equation:

°

F = 1.8 (°C) + 32

Chemical concentration in water is expressed in milligrams per liter (mg/L) and micrograms per liter (μg/L).

Abbreviations

The following terms are abbreviated in this report:

Aberdeen Proving Ground (APG) below land surface (bls)

1,2–Dichloroethene (1,2–DCE) Carbon tetrachloride (CT)

Chloroform (CF) Hexachloroethane (HCA)

1,1,2,2–Tetrachloroethane (TeCA) Trichloroethene (TCE)

Vinyl chloride (VC) volatile organic compounds (VOCs)
Abstract 1

Changes in Ground-Water Quality in the Canal Creek Aquifer 

Between 1995 and 2000–2001, West Branch Canal Creek Area,

Aberdeen Proving Ground, Maryland

By Daniel J. Phelan, William B. Fleck, Michelle M. Lorah, and Lisa D. Olsen

Abstract

Since 1917, Aberdeen Proving Ground, 

Maryland has been the primary chemical-warfare 

research and development center for the 

U.S. Army. Ground-water contamination has 

been documented in the Canal Creek aquifer 

because of past disposal of chemical and ordnance 

manufacturing waste. Comprehensive sampling 

for volatile organic compounds in ground water by 

the U.S. Geological Survey in the West Branch 

Canal Creek area was done in June–October 1995 

and June–August 2000. The purpose of this 

report is (1) to compare volatile organic compound 

concentrations and determine changes in the 

ground-water contaminant plumes along two cross 

sections between 1995 and 2000, and (2) to 

incorporate data from new piezometers sampled in 

spring 2001 into the plume descriptions.

Along the southern cross section, total concentrations of volatile organic compounds in 1995 

were determined to be highest in the landfill area 

east of the wetland (5,200 micrograms per liter), 

and concentrations were next highest deep in the 

aquifer near the center of the wetland (3,300 

micrograms per liter at 35 feet below land surface). When new piezometers were sampled in 

2001, higher carbon tetrachloride and chloroform 

concentrations (2,000 and 2,900 micrograms per 

liter) were detected deep in the aquifer 38 feet 

below land surface, west of the 1995 sampling. A 

deep area in the aquifer close to the eastern edge of 

the wetland and a shallow area just east of the 

creek channel showed declines in total volatile 

organic compound concentrations of more than 25 

percent, whereas between those two areas, concentrations generally showed an increase of 

greater than 25 percent between 1995 and 2000.

Along the northern cross section, total 

concentrations of volatile organic compounds in 

ground water in both 1995 and 2000 were 

determined to be highest (greater than 2,000 

micrograms per liter) in piezometers located on 

the east side of the section, farthest from the creek 

channel, and concentrations were progressively 

lower at piezometer locations closer to the creek 

channel. Total volatile organic compound concentrations increased more than 25 percent in 

some areas in the middle depths of the aquifer; 

however, it could not be determined if a defined 

plume was moving farther downgradient along 

ground-water flow paths toward the creek channel, 

or vertically downward because of density 

differences within the aquifer.

Introduction

Since 1917, Aberdeen Proving Ground (APG), Maryland 

(fig. 1) has been the primary chemical-warfare research and 

development center for the U.S. Army. In 1990, APG was 

placed on the National Priorities List established under the 

Comprehensive Environmental Response, Compensation, 

and Liability Act of 1980, and the Army and the U.S. 

Environmental Protection Agency, Region III, signed an 

Interagency Agreement for investigation and remediation of 

the Canal Creek area and other areas at APG.

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

with the U.S. Army Environmental Conservation and 

Restoration Division, began a study in 1992 to determine the 

distribution, fate, and transport of chlorinated volatile 

organic compounds (VOCs) in ground water in an area of the 

wetland along the West Branch Canal Creek, APG, Maryland 

(fig. 1). The study area is a contaminated site that is part of, 

and downgradient from, known contaminant disposal areas. 

 
2 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

Purpose and Scope

The purpose of this report is (1) to compare VOC 

concentrations and determine changes in the ground-water 

contaminant plumes along two cross sections between

June–October 1995 (Lorah and others, 1997) and

June–August 2000, and (2) to incorporate data from new 

piezometers sampled in spring 2001 into the plume descriptions. Two cross sections through the wetland area showing 

the distribution of total VOCs, 1,1,2,2–tetrachloroethane 

(TeCA), trichloroethene (TCE), carbon tetrachloride (CT), 

and chloroform (CF) in 1995 and in 2000–2001 are presented. Cross sections showing concentrations of CT were 

not included in Lorah and others (1997), but are presented in 

this report for both 1995 and 2000–2001.

Description of Study Area

The West Branch Canal Creek study area is in the northwest section of the Edgewood area of APG (fig. 1). The 

area is a mix of wooded and tidal wetland areas, some open 

fields, abandoned buildings, office buildings, and warehouses. When precipitation is heavy, water collects in 

wooded areas where drainage is poor because of the low soil 

permeability. Land-surface altitudes range from a maximum of 150 ft (feet) above sea level at the northern edge of 
Introduction 3

the drainage basin in Edgewood (fig. 1), to sea level in the 

tidal part of the stream.

The climate is temperate and moderately humid. 

Because of the proximity of APG to the Chesapeake Bay 

and the Atlantic Ocean, winters are milder and humidity is 

higher than farther inland. Average annual precipitation 

ranges from 39 to 45 in. (inches) (Durda and others, 1991, 

p. 2–7). The mean daily temperature is 33.8 °

F (degrees 

Fahrenheit) in the winter and 75.2 °

F in the summer (Durda 

and others, 1991, p. 2–7; Lorah and others, 1996).

Floating walkways were installed in 1994 along the two 

sections to allow access to part of the wetland along the 

West Branch Canal Creek (fig. 2). Access to the wetland 

beyond the walkway area is limited by tall, dense marsh 

vegetation (primarily Phragmites), and soft mud that is 

typically more than 8 ft deep. Surface-water depths can 

range from 0 to about 5 ft, depending on location, tides, and 

winds. 
4 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

Hydrogeologic Setting

The geology of the Canal Creek area is characterized by 

thick, wedge-shaped deposits of unconsolidated Coastal 

Plain sediments that dip southeastward (fig. 3). The Canal 

Creek aquifer ranges from 30 to 70 ft thick in this area and is 

unconfined in the wetland area (Lorah and Clark, 1996). 

The lower confined aquifer, which underlies the approximately 60-ft-thick confining unit beneath the Canal Creek 

aquifer, is not known to be contaminated (Lorah and 

Vroblesky, 1989; Lorah and Clark, 1996; Oliveros and 

Vroblesky, 1989). The 60-ft-thick confining unit appears to 

prevent contamination in the Canal Creek aquifer from 

migrating downward into deeper aquifers. 

Within the West Branch Canal Creek study area, the 

Canal Creek aquifer sediments consist of medium- to coarsegrained sand and gravel, interfingered with thin layers, or 

lenses, of clay and silt. East of the wetland, the aquifer is 

overlain by landfill material and the sediments of the upper 

confining unit. Within the West Branch Canal Creek wetland area, the aquifer is overlain by fine-grained organic-rich 

wetland sediments, which range from about 6 to 25 ft thick. 

The wetland sediments consist of peat, clay, silt, sandy clay, 

and clayey sand (Olsen and others, 1997).
Introduction 5

Two hydrogeologic cross sections in the West Branch 

Canal Creek area are described in this report. The piezometers shown in the sections were installed during different 

drilling phases between 1993 and 2000. The southern 

section is designated as A–A′′, and includes data from new 

piezometer nests installed west of the creek channel in 2000 

(fig. 2). On the basis of data collected from these new 

piezometers, the A–A′′ section described in this report 

extends farther west than in previous reports describing the 

contamination in the wetland.

The northern section is designated as C–C ′, and no 

additional piezometer nests were installed in this area since 

previous reports describing the hydrogeology were published. The locations of these sections are shown in figure 2, 

and the hydrogeology of the two sections, and the depths of 

the piezometer screens used for measuring water levels and 

water quality along the sections are presented in figures 4 

and 5. 

Ground water in the Canal Creek aquifer generally flows 

laterally and upward from both sides of the creek toward the 

center of the wetland. Discharge of ground water from the 

Canal Creek aquifer occurs through the wetland sediments 

into the creek and surrounding wetland areas (Lorah and 

Clark, 1996). Anaerobic biodegradation of the VOCs from 

the Canal Creek aquifer occurs in these wetland sediments 

(Lorah and Clark, 1996).

The head distributions and generalized ground-water 

flow directions for the A–A′′ section in the Canal Creek 

aquifer and the overlying wetland sediments at high tide on 

December 3, 2001 are shown in figure 6. Head differences, 

calculated from measurements in piezometers between high 

and low tide on December 3, 2001 along the section were 

negligible; therefore, only high tide data are shown in figure 

6. The ground-water divide representing the convergence of 

ground-water flow from the east and west sides of the wetland is located near the center of the wetland, in the general 

vicinity of piezometer nests WB41 and WB42 (fig. 6). 

Ground-water flow in the wetland area is primarily vertical 

toward the wetland surface. The creek channel meanders 

cross the wetland area (figs. 1 and 2); however, the center of 

the wetland and not the location of the creek channel appears 

to be the center point of ground-water discharge (fig. 6).

Site History

Most of APG’s chemical-manufacturing and munitionsfilling plants were concentrated in the area of the West 

Branch and East Branch Canal Creek. After World War II, 

large-scale production and filling operations declined 

sharply, and many of the manufacturing plants have been 

demolished or abandoned.

Chlorinated organic solvents, which were used as decontaminating agents and degreasers, were common waste products from the manufacturing and filling plants in the Canal 

Creek area. Wastes from many of these activities were 

discharged into Canal Creek directly through overland runoff 

or through sewer discharges until the late 1970s (Lorah and 

Clark, 1996). The various disposal activities also resulted 

in ground-water contamination in the Canal Creek aquifer 

along the West Branch Canal Creek. Some of these wastes 

remain in the Canal Creek aquifer and continue to reach the 

wetland indirectly through the discharge of contaminated 

ground water. In the late 1960s, potentially contaminated 

construction materials from the demolition of some of these 

manufacturing plants were pushed out into the Canal Creek 

wetland, creating landfills where there originally had been 

natural wetland sediments (Lorah and Vroblesky, 1989; 

Lorah and Clark, 1996). No known wastes have been discharged to the wetland or creek from the manufacturing 

plants or sewer systems within at least the last two decades.

CT, CF, TeCA, TCE, and Hexachloroethane (HCA) are 

the major contaminants found in the Canal Creek aquifer in 

the West Branch Canal Creek wetland. Organic solvents, 

such as CT, TeCA, and TCE probably were the most common wastes produced in large quantities from manufacturing, filling, and other miscellaneous activities in the Canal 

Creek area. The chemical agent chloracetophenone (CN, a 

tear gas) was manufactured in two different buildings east of 

the West Branch Canal Creek wetland between 1921 and 

1944. Several million pounds of CF, CT, and benzene were 

handled at both CN plants during the manufacturing process. 

HCA was a constituent used in the manufacturing of smoke 

mixtures in the vicinity, and CT was used in the reduction 

process. The history of the manufacturing and disposal 

activities in the Edgewood area of APG is described in detail 

in Nemeth (1989).

Description of Contaminant Plumes and Potential 

Source Areas

The sewer lines and landfill areas that likely are the 

sources of contamination along the East and West Branch 

Canal Creek previously were described by Nemeth (1989) 

and Lorah and Clark (1996). Sewer lines that reportedly 

were used to discharge wastes from the various chemical 

manufacturing facilities in the study area discharged to the 

West Branch Canal Creek wetland in the general vicinity of 

the floating walkways (fig. 2). Some of the sewer lines 

leaked organic solvents directly into the aquifer before discharging to the wetland (Nemeth, 1989). The ends of the 

sewer lines now are buried and have not been located. 

One sewer line (identified as part of sewer line number 6, 

Nemeth, 1989, p. 169) carried wastes from the World War II 

chlorine plant and discharged to the east side of the wetland 

in the general vicinity of well nest CC27 (fig. 2). The 

chlorine plant was thought to be a large source of solvents; 

however, other chemical-agent manufacturing plants also 

could have discharged wastes to sewer line 6. Chemical 

wastes from the manufacturing activities also were transported in drums or other containers to the edges of the 

wetland and disposed of at various locations in the area 

(Nemeth, 1989).

Ground-water contamination in the West Branch Canal 

Creek study area appears to be present in two overlapping 

contaminant plumes, based on the locations of the centers of 

concentrations, and differences in relative proportions of the 

compounds in the plumes. TeCA and TCE are the compounds most associated with plume 1, and are located 
6 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD
Introduction 7

predominantly along the C–C ′ section. CF and CT are the 

compounds most associated with plume 2, and are located 

predominantly along section A–A′′ and other sites south of 

the section. Samples from well nest CC27, which originally were included along the A–A′′ section, are more indicative of concentrations in plume 1. 

In 1995, the highest concentrations of VOCs in plume 2 

along the A–A′′ section (fig. 4) were located near the center 

of the wetland near piezometer WB28F (screened at 

34.5–35 ft below land surface, or bls), and on land at well 

CC27A (screened at 18–23 ft bls). Along the C–C ′ section, 

the highest concentrations of VOCs (primarily TeCA and 

TCE) in plume 1 were located near the eastern edge of the 

wetland near piezometer WB32B (screened at 14.5 ft bls) 

(fig. 5). The VOCs with the highest concentrations in 

ground water at WB28F were CT and CF. The VOCs with 

the highest concentrations in ground water at well CC27A 

were TeCA and TCE (the same compounds detected 

primarily along section C–C ′ in plume 1). Section A–A′′

intersects plume 2; however, the highest concentrations of 

CT and CF found to date were measured south of the A–A′′

section at sites HP01 and HP13 (fig. 2; Phelan, Senus, and 

Olsen, 2001). 

The differences in concentrations and relative proportions of TeCA, TCE, CT, and CF between piezometers representing plume 1 and plume 2 in both 1995 and 2000 are 

shown in figure 7. The highest concentrations in each of the 

two plumes are from different compounds. The plumes 

likely originated from two different sources (Lorah and 

others, 1997); however, ground-water samples indicate different degrees of intermixing caused by decades of transport 

by ground-water flow into the wetland areas. 
8 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD
Introduction 9

The sites where the highest concentrations of contaminants were found in the ground water were at HP01 and 

HP13 (fig. 2), just south of the A–A′′ section (Phelan, Senus, 

and Olsen, 2001). HCA (a waxy solid used as a component 

of smoke agents), CF, and CT were the compounds with the 

highest concentrations. Waste HCA likely was codisposed 

with waste CF and CT because these two solvents were used 

in the local manufacturing processes and would have aided 

in dissolving the HCA prior to disposal into sewer lines. 

Contaminants that were present in lower concentrations in 

that vicinity were TCE and TeCA, which could have been 

disposed of in the area or produced by degradation of 

HCA, or both. Phelan, Senus, and Olsen (2001) measured 

high concentrations of HCA (up to 10,000 μg/L, or micrograms per liter), CT (up to 29,000 μg/L), and CF (up to 

23,000 μg/L) in the Canal Creek aquifer at site HP01 at 

depths of 12–27 ft bls.

Previous Investigations

During 1977–78, the U.S. Army Toxic and Hazardous 

Materials Agency performed the first survey of the soil, 

sediment, ground water, and surface water of the Edgewood 

area of APG (Nemeth and others, 1983). An entire facility 

assessment was conducted by Nemeth (1989), in which he 

documented site history, ordnance and chemical manufacturing, filling, and support activities. Nemeth (1989) 

also identified the approximate locations of sewer lines in 

the Canal Creek area that were shown in historical APG 

facility drawings. These leaky sewer lines were the origin 

of much of the ground-water contamination in the study 

area.

A study conducted by the USGS during 1985–92 

described the hydrogeology of the Canal Creek area, and 

determined that a large ground-water contaminant plume 

was present in the Canal Creek aquifer along the West 

Branch Canal Creek. The study also showed that the contaminated ground water probably was discharging to the 

creek and the surrounding freshwater wetlands (Lorah and 

Clark, 1996, fig. 2). Major contaminants included the 

chlorinated VOCs TeCA, TCE, and CT, which are common 

industrial solvents used in the area.

The effects of natural attenuation on VOCs in ground 

water discharging through the fine-grained wetland sediments were determined by the USGS in an investigation conducted from 1992 to 1996 (Lorah and others, 1997). Biodegradation and sorption were shown to be important 

mechanisms for natural attenuation of VOCs in the wetland 

sediments. Lorah and others (1997) also discussed groundwater flow and distribution of VOCs in 1995 along what is 

referred to in this report as the A–A′′ and C–C ′ sections. 

Those data are the basis for the comparisons to 1995 conditions presented here.

The relatively thin layers of wetland sediments (ranging 

from 6 to 25 ft) are critical in reducing contaminant concentrations and the toxicity of ground water before it discharges to the wetland surface and the creek. Hydrogeologic, water-quality, and sediment-quality data collected 

by the USGS between 1992 and 1996 in the West Branch 

Canal Creek area are presented in Olsen and others (1997). 

Reports by Olsen and others (1997) and Spencer and others 

(in press) present the ground-water quality data, and describe 

methods for the collection, interpretation, and quality 

assurance of the water-quality data collected in the West 

Branch Canal Creek area from 1992 to 2001.

Continuous cores and ground-water samples from the 

Canal Creek aquifer were collected in remote locations in the 

Canal Creek wetland during 2000 using a hovercraft-mounted vibracore drill rig called a “Hoverprobe.” The lithologic 

data collected from the 5 coreholes and the 12 ground-water 

profiling sites are presented in Phelan, Senus, and Olsen 

(2001). Total VOCs in water from the upper part of the 

aquifer at two sites ranged from about 15,000 to greater than 

50,000 μg/L, whereas samples from other sites showed no 

ground-water contamination (Phelan, Senus, and Olsen, 

2001).
10 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

The distribution and occurrence of VOCs in surface 

water in the Canal Creek area were described by Olsen and 

Spencer (2000), and Phelan, Olsen, and others (2001). As 

many as 13 different VOCs were detected in surface-water 

samples collected in 1999 and 2000. Concentrations of 

individual VOCs in surface-water samples ranged from 

below the reporting limit of 0.5 μg/L to a maximum of 

50.2 μg/L for chloroform.

Cross sections with VOC concentrations for the 1995 

ground-water data presented in this report are from Lorah 

and others (1997). Tables of the 1995 VOC data, in addition 

to the inorganic constituents and physical parameters, are 

presented in Olsen and others (1997). Tables of groundwater VOC data from 2000–2001 used in this report are 

included in Spencer and others (in press).

Acknowledgments

The authors thank the following people for their important contributions to this investigation.

• John Wrobel of the U.S. Army Environmental 

Conservation and Restoration Division, APG, and 

Allison O’Brien and Amy Burgess, contractors for 

APG, provided project and logistical support.

• Peter Pritchard and the crew from the Aberdeen Test 

Center, APG, provided and installed the walkways and 

floating walkways in the wetland study area.

The authors also thank the following USGS personnel 

who assisted in the 2000–2001 investigation and report:

• Michael Senus, Linda Jo Dyer, Mastin Mount, 

Joseph Beman, Julie Kirshtein, Jonathan Johnson, and 

Anita Anderson.

• Tracey Spencer and Lisa Olsen analyzed the VOC 

samples at the USGS laboratory.

• Michael Bradley of the USGS Tennessee District and 

James Adamski of the USGS Florida District provided 

technical reviews for this report.

• Valerie M. Gaine for editorial review, Timothy W. 

Auer for graphics, and Donna R. Knight for layout of 

the report.

In addition, the following personnel from the U.S. Air 

Force Research Laboratory, Environmental Security 

Technology Certification Program, Tyndall Air Force Base, 

Florida, also assisted in the summer 2000 data collection:

• David Burris, Christopher Antworth, Elia Burr, and 

Robert Nichols. 

Methods of Investigation

 Ground-water samples were collected from a variety of 

4-in. wells, 2-in. wells, 1-in. piezometers, 0.75-in. drivepoint piezometers, and 0.25-in. piezometers, with depths 

ranging from 1 ft to 45.5 ft bls, along two cross sections 

within the study area. Descriptions of the wells and 

piezometers used in this study are listed in the Appendix. 

The 0.75-in. drive-point piezometers were installed in nests 

of 5 to 10 piezometers along the A–A′′ and C–C ′ sections 

(fig. 2), which generally are aligned parallel to the groundwater flow paths. In piezometer and well numbers, the 

prefix "WB" denotes West Branch, "CC" denotes Canal 

Creek, and "HP" denotes hoverprobe sampling sites. The 

relative depth intervals are identified by letter codes at the 

end of the numbers. The letter “A” corresponds to the 

shallowest, the letter “B” corresponds to the next shallowest, 

and so forth, except for piezometers WB33Y and WB33Z, 

which are 0.25-in. diameter piezometers installed in 1999 

that were screened shallower than piezometer WB33A. 

Piezometer nests WB19 to WB37 are composed of 0.75-in. 

diameter piezometers, and were installed between July 1994 

and February 1995. Piezometer nests WB41 and WB42 

are 1-in. diameter piezometers that were installed in 

November 2000 to further define the extent of the contamination along the A–A′′ section west of the creek 

channel.

The A–A′ section presented in Lorah and others (1997), 

extended from piezometer nests WB28 on the west to WB20 

on the east. In this report, the original A–A′ section has 

been expanded to the west to piezometer nest WB19 (fig. 2). 

The west end of the section at WB19 has been renamed as A, 

the nest at WB28 has been renamed A′, and the east end at 

WB20 has been renamed A′′ . The previous A–A′ section is 

referred to in this report as A′–A′′, and the new longer cross 

section is now A–A′′ (fig. 2).

The C–C ′ section is upstream of section A–A′′, and 

includes an area east of the creek channel. Piezometers 

WB33Y and WB33Z are the only piezometers in that section 

that were added between 1995 and 2000 and used in this 

report. The hydrogeology of the A–A′′ and C–C ′ sections, 

and the locations and depths of piezometer nests from which 

the ground-water samples were collected, are shown in 

figures 4 and 5, respectively.

Ground-water samples collected for organic constituents 

were analyzed at the USGS on-site laboratory at West 

Branch Canal Creek. VOC samples were analyzed using 

purge-and-trap gas chromatography with a mass-selective 

detector. Descriptions of the sampling methods and results 

of the quality-assurance methods for the data presented in 

this report are described in detail in Lorah and Clark (1996), 

Olsen and others (1997), Spencer and others (in press), 

Phelan, Senus, and Olsen (2001) and Phelan, Olsen, and 

others (2001). Olsen and others (1997) reported that the 

mean relative percent differences (RPDs) between duplicate 

organic compound concentrations were less than 15 percent 

for samples analyzed at the on-site laboratory. Samples 

with the highest RPDs tended to be samples in which analyte 

concentrations were less than 10 μg/L. Spencer and others 

(in press) found that for the 2000–2001 data, bromomethane 

and toluene analyzed at the on-site laboratory both had 

relatively high median RPDs (58 percent and 39 percent, 

respectively), compared to the other organic compounds. 

All other organic compound median RPDs for the 2000 data 

were below 12.2 percent.
Changes in Ground-Water Quality Between 1995 and 2000–2001 11

Changes in Ground-Water Quality Between 

1995 and 2000–2001

The following sections present comparisons showing the 

changes in the ground-water contaminant plumes along 

sections A–A′′ and C–C ′ between 1995 (Lorah and others, 

1997) and 2000–2001 (Spencer and others, in press). The 

general ground-water flow patterns described by Lorah and 

others (1997) reflect steady-state flow conditions with only 

slight seasonal variations because there has been no appreciable pumping or changes in hydrologic stresses on the Canal 

Creek aquifer in the study area since about 1968. Therefore, 

no changes in the overall direction and rate of the movement 

of the ground water affecting the contaminant plumes were 

anticipated for the period 1995–2001. The present steadystate flow conditions do not mean that plumes 1 and 2 have 

not moved, however, as contamination will tend to move 

from the source areas along the ground-water flow paths in 

the dissolved aqueous phase to discharge areas, and more 

dense non-aqueous phase liquid (DNAPL) can move downward in the aquifer contrary to the direction of ground-water 

flow. The rate of average linear velocity of ground-water 

flow in the Canal Creek aquifer in this area was calculated to 

be 3 ft/yr (feet per year) by Lorah and others (1997). The 

compounds HCA, TeCA, TCE, CT, and CF each have 

specific gravities that range from 1.46 to 2.09, which means 

that these compounds in the pure product state would tend to 

sink in the aquifer. Lorah and others (1997) documented 

seasonal changes in VOC concentrations in ground water. 

This report compares the concentrations of VOCs in ground 

water measured during the summers of 1995 and 2000 (and 

May 2001 for new piezometer nests WB41 and WB42) to 

exclude the possible effects of seasonal changes.

Comparison of Maximum Concentrations

The maximum concentrations of the major VOCs detected at each piezometer nest along sections A–A′′ and C–C ′ 

that were sampled in both 1995 and 2000 are compared in 

figure 8. Ground-water samples collected from piezometer 

nests WB41 and WB42 and piezometers WB33Y and 

WB33Z that were installed after 1995 were not included in 

this comparison. Maximum concentrations in each piezometer nest are used for comparison, regardless of variability 

with depth, in order to compare the magnitude of the contamination problem and to compare overall trends in contaminant concentrations over time and distance.

Along section A–A′′, the maximum concentrations of CT 

and CF (identified previously as the two major VOCs found 

in plume 2) were fairly consistent east of the creek channel 

(with the exception of well CC27, which is located farther 

north in the landfill area east of the wetland). At piezometer 

WB28F (screened from 34.5 to 35 ft bls), west of the creek 

channel, maximum concentrations of CT and CF generally 

were five to six times greater than the concentrations from 

piezometers east of the creek (WB27 through WB20) in 

both 1995 and 2000 (fig. 8). Maximum CT and CF concentrations for piezometer WB28F in 2000 were 770 and 

1,730 μg/L, respectively. Ground-water samples collected 

by Phelan, Senus, and Olsen (2001) at hoverprobe site HP01 

had CT and CF concentrations of 29,000 (at 17 ft bls) and 

23,100 μg/L (at 37 ft bls) respectively, indicating that these 

sites are closer to the source of the contaminants associated 

with plume 2.

Along section C–C ′, maximum concentrations of TeCA 

and TCE (identified previously as the two major VOCs in 

plume 1) and total VOCs in ground water generally declined 

progressing westward toward the creek channel in both 1995 

and 2000. The concentrations of CT and CF along section 

C–C ′, primarily associated with plume 2, generally did not 

decrease westward toward the creek channel in either 1995 

or 2000 (fig. 8). 

Distribution of Volatile Organic Compounds

Cross sections showing the distribution of total VOCs, 

TeCA, TCE, CT, and CF concentrations in ground water in 

1995 and 2000–2001 illustrate changes in the extent of the 

contaminant plumes. Data collected from piezometers 

installed after 1995 are included in the cross sections for 

2000–2001. Two 0.25-in. diameter piezometers (WB33Y 

and WB33Z) were installed in 1999 along the C–C ′ section 

to measure VOC concentrations in shallow ground water 

(2 ft and 4.5 ft bls, respectively) at the edge of the wetland 

where wetland sediments are thin, and daily flooding by high 

tides typically does not occur. Two additional piezometer 

nests (WB41 and WB42) installed on the west side of the 

creek along section A–A′′ were sampled in spring 2001 to 

further define the extent of the contaminant plume between 

piezo-meter nests WB19 and WB28 (fig. 4).

Section A-A’’ Along section A–A′′, piezometer nests 

WB19, WB21-WB25, WB28, WB41, and WB42 are in an 

area that is flooded by high tides, where the land surface 

typically is exposed at low tide. Sites WB26 and WB27 are 

in the creek channel and land surface is almost always below 

the creek level. Well nest CC27 and piezometer nest WB20 

are located east of the wetland at a higher elevation and were 

drilled through the fill material (fig. 4).

Total Volatile Organic Compounds (VOCs)—In 1995, total 

concentrations of VOCs along section A′–A′′ were highest 

in the landfill area east of the wetland (5,200 μg/L in well 

CC27A at 23 ft bls), and concentrations were next highest 

deep in the aquifer (3,300 μg/L at 35 ft bls) immediately 

west of the creek channel at WB28F (figs. 8 and 9a). When 

additional piezometers were installed in 2000 and sampled in 

2001 west of piezometer nest WB28, VOC concentrations 

along the A–A′′ section deep in the aquifer near the center of 

the wetland were higher than the concentrations at CC27A 

(fig. 9b). In 2000, Phelan, Senus, and Olsen (2001) detected 

even higher concentrations of total VOCs in ground water 

directly south of the A–A′′ section (50,700 μg/L at a depth 

of 12 ft bls) at site HP13 next to the creek channel about 

75 ft south of piezometer nest WB28, and at site HP01 

(50,100 μg/L at a depth of 17 ft bls), about 120 ft south of 

piezometer nest WB26 (fig. 2). The total VOC concentration of greater than 50,000 μg/L indicates the probable presence of DNAPL in the Canal Creek aquifer south of the 
12 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD
Changes in Ground-Water Quality Between 1995 and 2000–2001 13
14 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD
Changes in Ground-Water Quality Between 1995 and 2000–2001 15
16 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

A–A′′ section and close to site HP01.

Data from piezometer nests WB41 and WB42 show that 

the mapped extent of the VOC plume stretches west beyond 

the creek channel and piezometer nest WB28 (fig. 9b), 

described by Lorah and others (1997). The contaminant 

plume does not appear to reach piezometer nest WB19, 

which has consistently shown no evidence of contamination 

in samples collected between 1995 and 2000. Lorah and 

others (1997) found that 1995 concentrations of VOCs in 

samples from site WB19 were all less than 4 μg/L. In 2000, 

concentrations of VOCs in all samples from site WB19 were 

less than 1 μg/L (Spencer and others, in press). Two of the 

hoverprobe ground-water sampling sites located south and 

west of WB19 (sites HP03 and HP11, fig. 2) also had VOC 

concentrations in the Canal Creek aquifer that were below 

detection levels in ground water west of the A–A′′ section in 

April 2000 (fig. 2).

The areas where total VOC concentrations changed by 

more than 25 and 50 percent between 1995 and 2000 along 

the A′–A′′ section are shown in figure 9C. Declines in total 

VOC concentrations of more than 25 percent were found 

(1) in an area deep in the aquifer, extending from near piezometer nest WB28 to close to the eastern edge of the wetland 

(east of WB21G), (2) in a shallow area of wetland sediments 

just east of the creek channel (between WB23 and WB26), 

and (3) in 3 of 4 sample pairs in the aquifer at the east end of 

the section at sites CC27 and WB20. Total VOCs in the 

paleochannel deposits under the creek in the vicinity of 

WB27 and WB26 increased by more than 25 percent, as did 

concentrations in some middle and upper parts of the Canal 

Creek aquifer between the creek and the eastern edge of the 

wetland (fig. 9c).

1,1,2,2–Tetrachloroethane (TeCA)—The distribution of 

TeCA in ground water along section A–A′′ in 1995 and 

2000–2001 is shown in figures 10a and 10b. Contoured 

sections of the TeCA concentrations from the A–A′′ section 

for both 1995 and 2000–2001 indicate a plume in the top half 

of the aquifer spreading horizontally from below the fill 

material, past the eastern edge of the wetland toward the 

base of the wetland sediments at about 10 to 12 ft bls near 

the creek channel. Data from 2001 indicate that the plume 

extends west past WB41, but not as far as WB19 (fig. 10b). 

The highest concentration of TeCA along the A–A′′ section 

is located in the landfill area at well CC27A (figs. 4, 10a–b). 

The highest concentrations of TeCA detected along the

A–A′′ section in the wetland were under the general area of 

the creek channel (fig. 10b). Much of the TeCA plume 

could have been impeded from moving farther downward 

into the aquifer by the clayey silt layer located below the 

screen in well CC27A (fig. 10a).

Trichloroethene (TCE)—The distribution of TCE in ground 

water along the A–A′′ section is shown in figures 11a and 

11b. As with TeCA, the highest concentrations of TCE were 

found primarily in the upper half of the Canal Creek aquifer, 

below the fill material. Lorah and others (1997) showed 

that the TCE plume extended westward beyond the creek 

channel (fig. 11a). Data from the new piezometer nests 

installed in 2000 shows that the TCE plume extends westward beyond site WB41 and deeper (fig. 11b), and is found 

at concentrations as high as those found below the fill 

material east of the wetland, even though the plume does not 

extend to site WB19. Based on the data from samples collected from well CC27, and from shallow and deep samples 

collected from the aquifer under the creek channel, there 

were no major changes in the TCE plume along the A′–A′′

section between 1995 and 2000.

Carbon tetrachloride (CT)—The distribution of CT in 

ground water along the A–A′′ section is shown in figures 

12a and 12b. The CT plume along the A′–A′′ section as 

mapped in 1995 (fig. 12a) showed a plume centered along 

the upper part of the Canal Creek aquifer in the wetland area, 

with a single likely unrelated high concentration (560 μg/L) 

deep in the aquifer at a depth of 35 ft in WB28 (fig. 12a). 

Based on the CT concentrations in samples from the same 

piezometers in 2000, the CT plume showed no substantial 

change in magnitude or location between 1995 and 2000. 

With the additional data from sites WB41 and WB42 in 

2001, however, there appears to be a more concentrated part 

of the CT plume located near the bottom of the Canal Creek 

aquifer at the center of the wetland at WB42F at a depth of 

38 ft (figs. 4 and 12b). This plume may have resulted from 

the dissolution of DNAPL that may have settled at or near 

the bottom of the Canal Creek aquifer. The CT measured in 

the deep plume (2,000 μg/L in WB42F) likely is associated 

with the high concentrations of CT (up to 29,000 and 30,900 

μg/L) discovered at the top of the Canal Creek aquifer (17 to 

16 ft bls) by Phelan, Senus, and Olsen (2001) at hoverprobe 

sites HP01 and HP13, respectively.

Chloroform (CF)—The distribution of CF in ground water 

along the A–A′′ section is shown in figures 13a and 13b. 

There appear to be only minor differences in the extent and 

magnitude of CF concentrations between 1995 and 2000 in 

ground water along the original section A′–A′′. In 1995, 

maximum CF concentrations in three piezometers screened 

in the upper part of the aquifer east of the creek channel 

were between 200 and 230 μg/L (fig. 13a); however, in 

2000–2001, no concentrations in that part of the aquifer were 

greater than 190 μg/L (fig. 13b).
Changes in Ground-Water Quality Between 1995 and 2000–2001 17

As with CT, the additional 2001 data from the new piezometers indicate a concentrated CF plume near the bottom of 

the Canal Creek aquifer west of the creek channel at piezometer WB42F. CF concentrations in ground water along the 

A–A′′ section are nearly twice as high as the CT concentrations in the respective ground-water samples (figs. 12b 

and 13b). A graph comparing molar concentrations of CF to 

CT in ground water along section A–A′′ in 2000–2001 is 

shown in figure 14a. The slope of the linear-regression line 

comparing CF to CT in ground water is 1.8. Both CF and 

CT were detected at lower concentrations in surface water at 

Canal Creek, but in the same proportions as were detected in 

ground water in the aquifer. A graph comparing the molar 

concentrations of CF to CT in surface water in the West 

Branch Canal Creek area in 1999–2000 is shown in figure 

14b (Phelan, Olsen, and others, 2001). These compounds 

may have been disposed of together as solvents from the 

manufacturing of the chemical-filled ordnance known to 

have been used in the area (Lorah and others, 1997). 

In addition, CT can degrade to CF, and then to methylene 

chloride and carbon dioxide in a sequential hydrogenolysis 

reaction under anaerobic conditions (Bouwer, 1994). The 

ground water in the Canal Creek aquifer generally is aerobic, 

whereas ground water in the wetland sediments is anaerobic. 

CT and CF concentrations were highest deep in the Canal 

Creek aquifer (2,000 and 2,900 μg/L respectively at 37–38 ft 

bls), west of the creek channel at piezometer WB42F (figs. 

12b and 13b). In samples collected from sites where CT and 

CF concentrations were greater than 1,000 μg/L, methylene 

chloride was found at concentrations ranging from 43 to 

91 μg/L (Spencer and others, in press). No CT, CF, or 

methylene chloride was detected in the two shallowest 

ground-water samples from sites WB41 and WB42. This 

lack of detection indicates that natural attenuation of CT and 

CF could be occurring as ground water is discharging 

vertically toward the surface water through the anaerobic 

wetland sediments; however, additional investigation is 

needed to confirm this hypothesis. If ground water from that 

part of the plume was discharging directly to surface water 

through any preferential flow paths, such as seeps at the edge 

of the wetland, without undergoing the sequential hydrogenolysis reaction under anaerobic conditions within the 

wetland sediments, then CT and CF would be expected to be 

found in the same proportions in surface-water samples 

reported by Phelan, Olsen, and others (2001) (fig. 14b).

Section C–C‘ Along section C–C ′, piezometer nests 

WB34-WB37 are in the area that is flooded by high tides, 

where land surface typically is exposed at low tide. Site 

WB33 is on dry land near the edge of the wetland sediments 

that may be flooded only once or twice a year, and site 

WB32 is east of the wetland in the fill material area (fig. 5).

Total Volatile Organic Compounds (VOCs)—Along section 

C–C ′, total concentrations of VOCs in ground water during 

1995 and 2000 were highest in piezometers farthest east of 

the creek channel (WB32 and WB33), and concentrations 

progressively were lower at piezometer locations closer to 

the creek channel (figs. 8, 15a–b). VOC concentrations 

typically were higher above the clay lens that generally is 

located between 19 and 24 ft bls than concentrations deeper 

in the aquifer below the lens (figs. 15a–b).

Total VOC concentrations in piezometers WB33Y

(2 ft bls) and WB33Z (4.5 ft bls) (installed in 1999, fig. 5) in 

March 2000 were 310 and 770 μg/L, respectively. In 

June 2000, piezometer WB33Y was dry, and total VOC concentrations in WB33Z were 870 μg/L (Spencer and others, in 

press). In both sampling rounds, TeCA and TCE were the 

primary contaminants at WB33Y and WB33Z; however, the 

degradation compounds cis–1,2–dichloroethene (1,2–DCE) 

and trans–1,2–DCE accounted for about one-third of the 

total VOCs in those samples (Spencer and others, in press), 

indicating at least some degradation of the parent compounds. The increase of total VOCS (from 770 to 870) in 

piezometer WB33Z is within the median RPD between 

duplicate samples, and the seasonal variability in the median 

concentrations of TeCA was reported by Lorah and others 

(1997) to be less than the variability expected from sampling 

and analytical precision. The interpretation of VOC contours along the C–C ′ section for 2000 incorporates the new 

data from WB33Y and WB33Z, causing a noticeable change 

in the contours close to the contact of the wetland sediments 

and land surface at the edge of the wetland between 1995 

and 2000 (figs. 15a–b). In addition, piezometer WB34D 

was not sampled in 1995, but was sampled in 2000. The 

inclusion of these data, combined with new data from 

WB33Y and WB33Z, resulted in substantial changes in 

contour interpretations along the C–C ′ section.

The areas where total VOC concentrations changed by 

more than 25 percent between 1995 and 2000 along the 

C–C ′ section are shown in figure 15c. In general, total 

VOC concentrations decreased more than 25 percent 

between 1995 and 2000 in areas close to the creek channel at 

both the top and the bottom of the aquifer (fig. 15c). Total 

VOC concentrations increased more than 25 percent in some 

areas in the middle depths of the aquifer.

Although figures 15a and 15b show concentrations above 

detection levels in the shallow piezometers (“A” depth, 

fig. 5), Lorah and others (1997, p. 67) showed that hydrogenolysis of the 1,2 DCE (produced from dichloroelimination of 

TeCA) was occurring in the shallow wetland sediments and 

that degradation products decreased below detection levels 

within 6 in. of land surface. 
18 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD
Changes in Ground-Water Quality Between 1995 and 2000–2001 19
20 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD
Changes in Ground-Water Quality Between 1995 and 2000–2001 21
22 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD
Changes in Ground-Water Quality Between 1995 and 2000–2001 23
24 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD
Changes in Ground-Water Quality Between 1995 and 2000–2001 25
26 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD
Changes in Ground-Water Quality Between 1995 and 2000–2001 27

 
28 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD
Changes in Ground-Water Quality Between 1995 and 2000–2001 29
30 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

 

1,1,2,2–Tetrachloroethane (TeCA)—The overall extent of the 

TeCA plume along the C–C ′ section changed little between 

1995 and 2000. The plume is located predominantly in the 

upper half of the Canal Creek aquifer, and is separated from 

the lower part of the aquifer by a clay layer roughly 19–23 ft 

below sea level (figs. 16a–b). The TeCA concentration in 

the deeper part of the aquifer at piezometer WB33F increased from 6 to 130 μg/L between 1995 and 2000, however (fig. 

16b). Lorah and others (1997) showed that in the vicinity of 

piezometers WB35A and WB35B, concentrations of TeCA 

 

 

decreased and concentrations of the anaerobic degradation 

compounds dichloroethane (DCE) and vinyl chloride (VC) 

increased in the wetland sediments between 3 ft and 0.5 ft 

bls. Between 0.5 ft bls and land surface, concentrations 

decreased to about the minimum detection levels for each 

compound. Results showed a significant variation in the 

total amount of degradation products, and this variation 

could be related to seasonal changes in temperature in the 

shallow sediments (Lorah and others, 1997). 
Changes in Ground-Water Quality Between 1995 and 2000–2001 31
32 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

Trichloroethene (TCE)—As with the TeCA plume along the 

C–C ′ section, the extent of the TCE plume is primarily in 

the upper half of the Canal Creek aquifer (figs. 17a–b). The 

TCE concentrations east of WB34 along the C–C ′ section 

generally increased from two to ten times between 1995 and 

2000; however, very few changes occurred within the 

wetland sediments above the aquifer, indicating that the 

anaerobic natural attenuation of TCE as described by Lorah 

and others (1997) is continuing to occur and was not affected 

by the increased concentrations in the eastern region of the 

plume. In addition, there was essentially no change in the 

low TCE concentrations below the clay lens approximately 

25 ft bls in the Canal Creek aquifer between 1995 and 2000. 

 
Changes in Ground-Water Quality Between 1995 and 2000–2001 33
34 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

Carbon tetrachloride (CT)—Contours of the 1995 and 2000 

CT data along the C–C ′ section are shown in figures 18a and 

18b, respectively. Below the upper confining unit in the top 

half of the Canal Creek aquifer in piezometer nests WB32 

and WB33 east of much of the wetland, CT concentrations 

decreased from as high as 21 μg/L in 1995 to 3.1 μg/L or 

less in 2000 (figs. 18a–b). There were two detections of CT 

from piezometers screened in the deeper half of the aquifer 

in 1995 (1.7 and 21 μg/L), and there were no detections in 

the deeper half of the aquifer in 2000 (at a detection limit of 

0.5 μg/L) (fig. 18b). The CT plume along the C–C ′ section 

is located in the upper half of the Canal Creek aquifer, in 

the vicinity of piezometer nests WB34, WB35, and WB36, 

and the plume has changed little in area and overall concentration in the wetland area between 1995 and 2000 (figs. 

18a–b). 
Changes in Ground-Water Quality Between 1995 and 2000–2001 35
36 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

Chloroform (CF )—Contours of the 1995 and 2000 CF data 

along the C–C ′ section are shown in figures 19a and 19b. 

CF concentrations in the lower half of the Canal Creek 

aquifer ranged from 0.36 to 110 μg/L in 1995; however, 

samples from the same piezometers in 2000 showed concentrations ranging from below the detection limit to only 

1 μg/L. CF concentrations in the upper half of the aquifer 

ranged from below the detection limit of 0.5 μg/L to 28 μg/L 

in 1995, and 35 μg/L in 2000. The location and range of 

concentrations in the CF plume in the upper half of the Canal 

Creek aquifer along the C–C ′ section did not change 

measurably between 1995 and 2000. 
Changes in Ground-Water Quality Between 1995 and 2000–2001 37

 
38 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

Summary and Conclusions

Since 1917, Aberdeen Proving Ground, Maryland, has 

been the primary chemical-warfare research and development center for the U.S. Army. Most of the chemicalmanufacturing and munitions-filling plants were concentrated in the area of the West Branch and East Branch Canal 

Creek. The U.S. Geological Survey, in cooperation with 

the U.S. Army Environmental Conservation and Restoration 

Division, began a study in 1992 to determine the distribution, fate, and transport of chlorinated volatile organic 

compounds in ground water from an area of the wetland 

along the West Branch Canal Creek.

The purpose of this report is to (1) compare volatile 

organic compound concentrations and determine changes in 

the ground-water contaminant plumes along two cross sections between June–October 1995 and June–August 2000, 

and (2) incorporate data from new piezometers sampled in 

spring 2001 into the plume descriptions. These two cross 

sections, A–A′′ and C–C ′, generally are aligned parallel to 

ground-water flow paths in the wetland, with the possible 

exception of the well site CC27 in section A–A′′.

Notable differences in the identities and concentrations 

of the predominant volatile organic compounds were 

observed between sections A–A′′ and C–C ′ in both 1995 

and 2000. Data from sections A–A′′ and C–C ′ and nearby 

sampling sites indicate that there are two overlapping 

contaminant plumes in the wetland, and that these plumes 

differ in chemical composition. Section C–C ′ is more 

representative of Plume 1, which is in the northern part of 

the study area, and section A–A′′ is more representative of 

Plume 2, which is in the southern part of the study area. In 

section C–C ′, 1,1,2,2–tetrachloroethane and trichloroethene 

had the highest concentrations of detected volatile organic 

compounds. In section A–A′′, carbon tetrachloride and 

chloroform had the highest concentrations of detected 

volatile organic compounds, with the exception of 1,1,2,2–

tetrachloroethane in well CC27A.

Along section A–A′′, total concentrations of volatile 

organic compounds in 1995 were highest in the landfill area 

east of the wetland (5,200 micrograms per liter at 23 feet 

below land surface in well CC27A) and concentrations were 

next highest deep in the aquifer (3,300 micrograms per liter 

at 35 feet below land surface) near the creek channel at 

piezometer WB28F. When additional piezometers were 

sampled in 2001 west of piezometer nest WB28, carbon 

tetrachloride and chloroform concentrations (2,000 and 

2,900 micrograms per liter, respectively) were higher deep in 

the aquifer (37–38 feet below land surface) at WB42 near the 

center of the wetland, than concentrations found at WB28F 

or well CC27A. An area deep in the aquifer close to the 

eastern edge of the wetland (east of piezometer WB21G), 

and a shallow area just east of the creek channel (between 

piezometers WB23 and WB26), showed decreases in total 

volatile organic compound concentrations of greater than 25 

percent while the area between those two zones generally 

showed an increase of more than 25 percent. The areas with 

the highest known concentrations of carbon tetrachloride 

(30,900 micrograms per liter at site HP13) and chloroform 

(21,500 micrograms per liter at site HP01) were measured in 

2000 along the creek channel and near the top of the Canal 

Creek aquifer, just south of the A–A′′ section.

Along section C–C ′, total concentrations of volatile 

organic compounds in ground water in both 1995 and 2000 

were highest in piezometers located farthest east of the creek 

channel (WB32 and WB33), and concentrations progressively decreased at piezometer locations closer to the creek 

channel. Volatile organic compound concentrations typically are higher above the clay lens that generally is located 

between 19 and 24 feet below land surface, than concentrations deeper in the aquifer below the lens. In general, total 

volatile organic compound concentrations decreased more 

than 25 percent between 1995 and 2000 in areas close to the 

creek channel at both the top and bottom of the aquifer (less 

than 8 feet and greater than 30 feet below land surface). 

Total volatile organic compound concentrations increased 

more than 25 percent in some areas in the middle depths of 

the aquifer; however, it could not be determined if a defined 

plume was moving farther downgradient along flow lines 

toward the creek channel, or vertically downward because of 

the density differences within the aquifer.

References Cited

Bouwer, E.J., 1994, Bioremediation of chlorinated solvents 

using alternate electron acceptors, in Norris, R.D., and 

others, Handbook of bioremediation: Ann Arbor, 

Michigan, Lewis Publishers, p. 149–175.

Durda, J., Turnham, B., and Kipp, T., 1991, Baseline risk 

assessment for eight selected study areas at Aberdeen 

Proving Ground: Fairfax, Virginia, ICF Technology and 

Clement International Corporation, v. 1, chapters 1–7, 

prepared for U.S. Army Toxic and Hazardous Materials 

Agency, Contract DAAA15–88–D–0009, Task Order 11 

[variously paged].

Lorah, M.M., and Clark, J.S., 1996, Contamination of 

ground water, surface water, and soil, and evaluation of 

selected ground-water pumping alternatives in the Canal 

Creek area of Aberdeen Proving Ground, Maryland: 

U.S. Geological Survey Open-File Report 95–282, 318 p.

Lorah, M.M., Olsen, L.D., Smith, B.L., Johnson, M.A., 

and Fleck, W.B., 1997, Natural attenuation of 

chlorinated volatile organic compounds in a freshwater 

tidal wetland, Aberdeen Proving Ground, Maryland: 

U.S. Geological Survey Water-Resources Investigations 

Report 89–4171, 95 p.

Lorah, M.M., and Vroblesky, D.A., 1989, Inorganic and 

organic ground-water chemistry in the Canal Creek area 

of Aberdeen Proving Ground, Maryland: U.S. 

Geological Survey Water-Resources Investigations 

Report 89–4022, 97 p.
References Cited 39

Nemeth, Gary, 1989, RCRA facility assessment report, 

Edgewood Area, Aberdeen Proving Ground, Maryland: 

U.S. Army Environmental Hygiene Agency, Waste 

Disposal Engineering Division, Aberdeen Proving 

Ground, Maryland, Project 38–26–0490–90, 929 p.

Nemeth, Gary, Murphy, J.M., Jr., and Zarzycki, J.H., 

1983, Environmental survey of the Edgewood Area of 

Aberdeen Proving Ground, Maryland: U.S. Army Toxic 

and Hazardous Materials Agency, Aberdeen Proving 

Ground, Maryland, Report DRXTH–AS–FR–82185,

276 p.

Oliveros, J.P., and Vroblesky, D.A., 1989, Hydrogeology 

of the Canal Creek area, Aberdeen Proving Ground, 

Maryland: U.S. Geological Survey Water-Resources 

Investigations Report 89–387, 71 p.

Olsen, L.D., Lorah, M.M., Marchand, E.H., Smith, B.L., 

and Johnson, M.A., 1997, Hydrogeologic, waterquality, and sediment-quality data for a freshwater tidal 

wetland, West Branch Canal Creek, Aberdeen Proving 

Ground, Maryland, 1992–96: U.S. Geological Survey 

Open-File Report 97–560, 267 p.

Olsen, L.D., and Spencer, T.A., 2000, Assessment of 

volatile organic compounds in surface water at

West Branch Canal Creek, Aberdeen Proving Ground, 

Maryland, 1999: U.S. Geological Survey Open-File 

Report 00–203, 15 p.

Phelan, D.J., Olsen, L.D., Senus, M.P., and Spencer, T.A., 

2001, Assessment of volatile organic compounds in 

surface water at Canal Creek, Aberdeen Proving Ground, 

Maryland, November 1999–September 2000: U.S. 

Geological Survey Open-File Report 01–292, 49 p.

Phelan, D.J., Senus, M.P., and Olsen, L.D., 2001, 

Lithologic and ground-water-quality data collected

using hoverprobe drilling techniques at the West Branch 

Canal Creek, Aberdeen Proving Ground, Maryland: 

U.S. Geological Survey Open-File Report 00–446, 43 p.

Spencer, T.A., Phelan, D.J., Olsen, L.D., and Lorah, 

M.M., in press, Ground-water and surface-water quality 

data for the West Branch Canal Creek, Aberdeen Proving 

Ground, Maryland, November 1999–May 2001: U.S. 

Geological Survey Open-File Report 01–420.
40 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

 

Appendix. Sampling locations for wells and piezometers in the West Branch Canal Creek

study area, Aberdeen Proving Ground, Maryland—Continued

Well

number

Site

identification

number

Hydrogeologic

unit

Well

diameter

(inches)

Screened

interval

(feet below

land surface)

Land surface

elevation

(feet above

sea level)

CC27A 392343076183301 Canal Creek aquifer 4.0 18.0–23.0 11.2 

CC27B 392343076183302 Canal Creek aquifer 4.0 35.0–40.0 11.4 

DP1-A 392346076183501 Wetland sediments, upper peat unit 2.0 1.9–2.9 1.20

DP1-B 392346076183502 Wetland sediments, lower peat unit 2.0 6.5–7.5 1.23

WB19A 392354076183701 Wetland sediments, upper peat unit .75 1.3–1.8 1.52

WB19B 392354076183702 Wetland sediments, upper peat unit .75 4.2–4.7 1.50

WB19D 392354076183704 Canal Creek aquifer .75 13.5–14.0 1.51

WB19E 392354076183705 Canal Creek aquifer .75 28.5–29.0 1.46

WB19F 392354076183706 Canal Creek aquifer .75 45.0-45.5 1.33

WB20A 392345076183101 Canal Creek aquifer .75 15.1–16.0 12.18

WB20B 392345076183102 Canal Creek aquifer .75 21.0–21.5 12.32

WB20E 392345076183105 Canal Creek aquifer .76 21.0–21.6 13.32

WB21A 392346076183301 Wetland sediments, lower clayey unit .75 1.5–2.0 3.00

WB21B 392346076183302 Canal Creek aquifer .75 6.5–7.0 3.10

WB21C 392346076183303 Canal Creek aquifer .75 13.5–14.0 2.74

WB21D 392346076183304 Canal Creek aquifer .75 17.5–18.0 3.14

WB21E 392346076183305 Canal Creek aquifer .75 29.5–30.0 3.10

WB21F 392346076183306 Canal Creek aquifer .75 36.0–36.5 3.10

WB21G 392346076183307 Canal Creek aquifer .75 45.0–45.5 3.25

WB22A 392342076183401 Wetland sediments upper peat unit .75 1.5–2.0 2.52

WB22B 392342076183402 Wetland sediments upper peat unit .75 7.0–7.5 2.62

WB22C 392342076183403 Canal Creek aquifer .75 13.0–13.5 2.52

WB22D 392342076183404 Canal Creek aquifer .75 17.0–17.5 2.47

WB22E 392342076183405 Canal Creek aquifer .75 22.0–22.5 2.53

WB23A 392341076183401 Wetland sediments, upper peat unit .75 0.5–1.0 1.05

WB23B 392341076183402 Wetland sediments, lower clayey unit .75 2.2–2.7 .77

WB23C 392341076183403 Wetland sediments, lower clayey unit .75 8.5–9.0 1.06

WB23D 392341076183404 Canal Creek aquifer .75 12.5–13.0 1.01

WB23E 392341076183405 Canal Creek aquifer .75 16.0–16.5 .92

WB23F 392341076183406 Canal Creek aquifer .75 21.0–21.5 1.00

WB24A 392343076183401 Wetland sediments, upper peat unit .75 0.9–1.4 1.85

WB24B 392343076183402 Wetland sediments, upper peat unit .75 3.0–3.5 1.77

WB24C 392343076183403 Wetland sediments, upper peat unit .75 5.5–6.0 1.75

WB24D 392343076183404 Canal Creek aquifer .75 12.5–13 1.64

WB24E 392343076183405 Canal Creek aquifer .75 16.5–17.0 1.85

WB24F 392343076183406 Canal Creek aquifer .75 28.0–28.5 1.80

Appendix. Sampling locations for wells and piezometers in the West Branch Canal Creek

study area, Aberdeen Proving Ground, Maryland

 [Site identification number represents the latitude, longitude, and sequence number within the cluster and is used for 

 tracking water-quality samples; –, no data]
Appendix 41

WB25A 392342076183502 Wetland sediments,upper peat unit 0.75 0.5–1.0 1.23

WB25B 392342076183503 Canal Creek aquifer .75 13.5–14.0 1.20

WB25C 392342076183504 Canal Creek aquifer .75 15.5–16.0 1.12

WB26A 392343076183502 Wetland sediments, upper peat unit .75 1.0–1.5 .38

WB26B 392343076183503 Wetland sediments, upper peat unit .75 2.5–3.0 .47

WB26C 392343076183504 Wetland sediments, upper peat unit .75 4.0–4.5 .20

WB26D 392343076183505 Wetland sediments, lower clayey unit .75 5.5–6.0 .33

WB26E 392343076183506 Paleochannel .75 8.8–9.3 .28

WB26F 392343076183507 Canal Creek aquifer .75 15.0–15.5 .33

WB26G 392343076183508 Canal Creek aquifer .75 19.5–20.0 .40

WB26H 392343076183509 Canal Creek aquifer .75 27.0–27.5 .50

WB27A 392343076183521 Wetland sediments, upper peat unit .75 1.0–1.5 -.92

WB27B 392343076183522 Wetland sediments, upper peat unit .75 3.2–3.7 -.97

WB27C 392343076183523 Wetland sediments, upper peat unit .75 4.5–5.0 -.98

WB27D 392343076183524 Paleochannel .75 8.2–8.7 -.88

WB27E 392343076183525 Canal Creek aquifer .75 15.0–15.5 -.96

WB27F 392343076183526 Canal Creek aquifer .75 18.0–18.5 -.90

WB27G 392343076183527 Canal Creek aquifer .75 26.0–26.5 -.90

WB28A 392345076183511 Wetland sediments, upper peat unit .75 1.2–1.7 .83

WB28B 392345076183512 Wetland sediments, upper peat unit .75 4.5–5.0 .84

WB28C 392345076183513 Wetland sediments, upper peat unit .75 9.0–9.5 .82

WB28D 392345076183514 Canal Creek aquifer .75 14.5–15.0 .89

WB28F 392345076183516 Canal Creek aquifer .75 34.5–35.0 .73

WB32B 392347076183202 Canal Creek aquifer .75 26.5–27.0 10.77

WB33Y – Wetland sediments, upper peat unit .25 1.9–2.0 2.96

WB33Z – Wetland sediments, upper peat unit .25 4.5–4.6 2.96

WB33A 392353076183301 Canal Creek aquifer .75 8.7–9.2 2.96

WB33B 392353076183302 Canal Creek aquifer .75 14.0–14.5 2.95

WB33F 392353076183306 Canal Creek aquifer .75 42.5–43.0 2.95

WB34A 392348076183410 Wetland sediments, upper peat unit .75 1.5–2.0 1.43

WB34B 392348076183411 Canal Creek aquifer .75 7.3–7.8 1.37

WB34C 392348076183412 Canal Creek aquifer .75 15.0–15.5 1.36

WB34D 392348076183413 Canal Creek aquifer .75 18.3–18.8 1.35

WB34E 392348076183414 Canal Creek aquifer .75 26.5–27.0 1.35

Appendix. Sampling locations for wells and piezometers in the West Branch Canal Creek

study area, Aberdeen Proving Ground, Maryland—Continued

Well

number

Site

identification

number

Hydrogeologic

unit

Well

diameter

(inches)

Screened

interval

(feet below

land surface)

Land surface

elevation

(feet above

sea level)
42 Changes in Ground-Water Quality in the Canal Creek Aquifer Between 1995 and 2000–2001, APG, MD

WB35A 392354076183402 Wetland sediments, upper peat unit 0.75 1.5–2.0 1.19

WB35B 392354076183403 Wetland sediments, upper peat unit .75 2.8–3.3 1.29

WB35C 392354076183404 Canal Creek aquifer .75 7.2–7.7 1.27

WB35D 392354076183405 Canal Creek aquifer .75 13.0–13.5 1.27

WB35E 392354076183406 Canal Creek aquifer .75 18.0–18.5 1.27

WB35F 392354076183407 Canal Creek aquifer .75 27.5–28.0 1.31

WB36A 392355076183402 Wetland sediments, upper peat unit .75 1.7–2.2 1.27

WB36B 392355076183403 Wetland sediments, upper peat unit .75 2.7–3.2 .99

WB36C 392355076183404 Canal Creek aquifer .75 7.1–7.6 1.04

WB36D 392355076183405 Canal Creek aquifer .75 13.0–13.5 .98

WB36E 392355076183406 Canal Creek aquifer .75 18.0–18.5 1.03

WB36F 392355076183407 Canal Creek aquifer .75 27.5–28.0 1.00

WB36G 392355076183408 Canal Creek aquifer .75 32.0–32.5 1.09

WB37A 392356076183402 Wetland sediments,upper peat unit .75 1.7–2.2 .76

WB37B 392356076183403 Wetland sediments, upper peat unit .75 2.5–3.0 .71

WB37C 392356076183404 Canal Creek aquifer .75 7.1–7.6 .72

WB37D 392356076183405 Canal Creek aquifer .75 13.5–14.0 .75

WB41A 392345076183601 Wetland sediments, upper peat unit 1.0 8.25–9.25 1.31

WB41B 392345076183602 Wetland sediments, upper peat unit 1.0 9.0–10.0 1.08

WB41C 392345076183603 Canal Creek aquifer 1.0 22.4–23.4 1.31

WB41D 392345076183604 Canal Creek aquifer 1.0 28.0–30.0 1.32

WB41E 392345076183605 Canal Creek aquifer 1.0 31.3–32.3 1.24

WB42A 392343076183601 Wetland sediments, upper peat unit 1.0 6.0–7.0 1.31

WB42B 392343076183602 Canal Creek aquifer 1.0 13.0–14.0 1.27

WB42C 392343076183603 Canal Creek aquifer 1.0 19.0–20.0 1.45

WB42D 392343076183604 Canal Creek aquifer 1.0 25.0–26.0 1.32

WB42E 392343076183605 Canal Creek aquifer 1.0 31.0–32.0 1.24

WB42F 392343076183606 Canal Creek aquifer 1.0 37.0–38.0 1.34

Appendix. Sampling locations for wells and piezometers in the West Branch Canal Creek

study area, Aberdeen Proving Ground, Maryland—Continued

Well

number

Site

identification

number

Hydrogeologic

unit

Well

diameter

(inches)

Screened

interval

(feet below

land surface)

Land surface

elevation

(feet above

sea level)