United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-01-005
April 2001
Issue No. 39
reatment
CONTENTS
Current Field Studies
on Phytoremediation
at Aberdeen Proving
Ground Pg. 1
Funnel-and-Gate
Treatment System
for Pesticide-
Contaminated Ground
Water Pg. 2
Iron Reactive Barrier
Used at Rocky Flats
Site
Pg-3
Technology Call for
Measurement of MTBE
in Ground Water Pg. 4
About this Issue
This issue highlights joint
partnerships among U.S. EPA
Regions and laboratories, other
Federal agencies, and private
industry to use innovative
technologies for remediating
sites with contaminated ground
water.'<^
Current Field Studies on
Phytoremediation at
Aberdeen Proving Ground
by Steven Hirsh,
U.S. EPA/Region 3
Phytoremediation is under evaluation as
a remedial technology for contaminated
ground water at the J-Field Superfund
site located on Aberdeen Proving
Ground (APG), MD. This five-year study
is conducted under a joint partnership
among the U.S. Army, U.S. EPA Region
3, and the U.S. EPA Environmental
Response Team Center as part of the U.S.
Department of Defense (DOD) efforts to
use emerging remediation technologies.
The success of conventional technolo-
gies such as soil washing, soil vapor
extraction, and pump and treat systems
had been found to be hindered signifi-
cantly by complex site conditions at
J-Field. These difficulties include the
presence of unexploded ordnance, a low
permeability aquifer, and a persistent
contaminant source fed by residual non-
aqueous phase liquids. Recent analysis
of in situ bioremediation processes
enhanced through phytoremediation
demonstrates that degradation of
chlorinated volatile organic compounds
(CVOCs) is occurring actively in the J-
Field study area.
APG is located along the western shore
of the Chesapeake Bay. Over the years,
military weapons testing has caused
extensive release of chemicals to ground
water and soil at J-Field, where disposal
activities took place in a 500- by 800-
foot area known as the toxic burning
pits. Significant levels of CVOCs were
detected in the area's ground water,
which flows from below the pits toward
an adjacent freshwater marsh. The
underlying aquifer is comprised of
interbedded, low permeability fine sands
and clayey silts that can sustain well
yields of only 0.3-1.0 gallons per
We want to hear from you.
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developments in innovative ground
water treatment technologies to
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minute. Low permeability sediments in
this area, coupled with relatively low
ground-water recharge, produce an
average ground-water flow velocity of
approximately 10-15 feet per year.
Phytoremediation was selected to reduce
CVOC mass loading to the marsh by
providing hydraulic containment of the
CVOC plume and overall CVOC mass
reduction. A pilot-scale study of this
technology began in 1996 with the
[continued on page 2]
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[continued from page 1]
planting of 183 hybrid poplar trees in a
U-shaped configuration surrounding the
burning pits. Earlier agronomic sampling
had indicated that the fast-growing, deep-
rooting characteristics of hybrid poplar
trees would make them suitable for this
area's soil characteristics, climate, and
hydrology.
Prior to planting, modeling was per-
formed to predict the time required for
the poplar trees to achieve aquifer
Ongoing sampling and analysis indicate
that successful results are being achieved
through phytoremediation in the study
area. Generally, by the time ground water
is discharged from J-Field to the adjoin-
ing marsh, essentially non-detect levels
of the primary contaminants (1,1,2,2-
tetrachloroethane and trichloroethane)
are reached (Table 1). Using very
sensitive sampling techniques, volatile
emissions from a small number of trees
can be measured; however, extensive air
monitoring has shown no measurable
volatiles in the ambient air.
Funnel-and-Gate Treatment
System for Pesticide-
Contaminated Ground Water
by Annie Godfrey, U.S. EPA/Region
4, Karl Hoenke, Chevron
Environmental Management
Company, and Dean Williamson,
CH2MHUI
A full-scale funnel and gate (F&G) system
began operating in 1998 at the Marzone
guperfund site near Tifton, GA, to treat
Table 1. Maximum Detected (.
Contaminant of Concern
1 , 1 ,2,2-tetrachloroethane
trichforoethene
cis- 1,2-dichforoethene
tetrachforoethene
trans- 1,2-dichforoethene
1 , 1 ,2-triehforoethane
vinyl chloride
ethene
Concentrations in
At J-Field
&KJ/L)
390,000
93,000
81,000
11,000
29,000
7,100
4,200
509
Study Area
Upon Marsh
Entry (ng/L)
15
47
36
non detect
11
2
7
36,400
restoration. Modeling estimates took into
account contaminant uptake rates as
determined by transpiration stream
concentration factors, transpiration rates,
and average contaminant concentrations
in ground water. Analytical modeling
also was used to position the poplar trees
for maximizing ground-water withdrawal
efficiency, taking into account the
ground-water flow rate, hydraulic
conductivity, hydraulic gradient, aquifer
thickness, and potential plume capture
width. In 1998, several trees that had died
were analyzed and replaced by additional
hybrid poplars and two native tree
species (tulip trees [Liriodendron
ttilipiferia] and silver maple [Acer
saccharinum]). Different methods were
used in this second round of planting to
encourage more extensive tree rooting.
Other potential impacts of
phytoremediation also are under evalua-
tion in the J-Field area. For example, to
assess the health and functioning of the
soil community in this area, soil samples
are taken periodically for nematode
identification and enumeration. In
addition, regular monitoring is con-
ducted to assess the effects of the poplar
trees on the ground water. Pending final
study results gained during 2001, it is
anticipated that EPA and DOD will
implement a full-scale phytoremediation
program at APG. For more information,
contact Steven Hirsh (EPA/Region 3) at
215-814-3352 or e-mail
hksh.steven@epa.gov.
groumfwater contaminated with pesticides""
and other organics. This passive treatment
system was selected as an alternative to the
pump and treat remedy (specified in the
site's record of decision), which may not be
effective at this site. The U.S. EPA/Region
4, Chevron Environmental Management
Company, and CH2M Hill have been
closely monitoring the F&G system's
performance, and have found that the
system is reducing total xylene and
pesticide concentrations by more than 99
percent.
Contaminants accumulated at the Marzone
site as a result of various pesticide formu-
lating activities that took place between
1950 and 1983. These contaminants
include DDT, toxaphene, atrazine, dieldrin,
chlordane, lindane, alpha-
benzenehexachloride (BHC), endosulfan,
methyl parathion, xylene, and ethyl
benzene. Analytical sampling indicated
total xylene concentrations as high as
20,000 ug/L and total BHC concentrations
of up to 4 ug/L in ground water. The
-affected shallow surficialaquifer, which
extends to approximately 20-25 feet below
ground surface, comprises primarily
interbedded silts and clays, with some
discontinuous sand lenses. Ground-water
flow velocities in this aquifer unit typi-
cally range from 10 to 20 feet per year.
Bench-scale testing of the capability of
various media to remove or degrade
hydrocarbons and the applicable pesticide
classes indicated that granular activated
carbon (GAC) was best suited to serve as
the system's adsorptive medium. Based on
factors such as residence time with the
GAC, surface loading rates,
constructability, life cycle costs, and
corrosion resistance, a gate design that uses
pre-cast vaults was selected.
[continued on page 3]
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[continued from page 2]
The F&G system comprises three three-
foot-square, 16-foot-deep concrete vessels
with interconnecting piping that allow for
operation of two vessels in series or in
parallel, with both up-flow and down-flow
modes. This configuration is intended to
accommodate changes in operational
modes or reactive media that may be made
during potential operation of the system
over several decades.
The results of ground-water analysis
conducted at the time of system start-up
demonstrated effective GAC performance
(Table 2). Currently, the system is treating
approximately 1 to 2 gallons of water per
minute. Overall analytical results indicate
that total xylene concentrations are
reduced from 15,000 to 20,000 ug/L in
the influent to less than 1 ug/L in the
effluent, and total BHC concentrations are
reduced from 1 to 4 ug/L to less than 0.05
ug/L.
Efforts also were made to use innovative ,
methods for construction and operation of
the F&G system. For example, to mini-
mize impacts on a nearby transportation
corridor and the surrounding community,
a vibrated beam method was used to
install the cutoff wall (funnel) instead of
soil-bentonite slurry walls, which typi-
cally introduce major surface disturbance.
An additional innovative method
(biopolymer slurry) was used to construct
the system's collection and discharge
trenches. This method eliminated the need
for trench boxes to support the side walls
and eliminated the need for personnel to
enter the trench.
Table 2. Groi
Parameter
xylene
ethylbenzene
a/p/ja-benzenehexachloride
feefa-benzenehexacHoride
lindane
dissolved iron
dissolved manganese
total organic carbon
total suspended solids
md Water Analysis a
Influent
16,000 Mg/L
2100 Mg/L
0.96 ug/L
0.89 Mg/L
0.80 ug/L
14 to 60 mg/L
1.5 to 3.0 mg/L
25 to 120 mg/L
12 to 52 mg/L
tStart-Up
Effluent
<2|Jg/L
<1 Mg/L
<0.03pg/L
<0.10 |jg/L
<0.20 Mg/L
30 mg/L (limited data)
3 mg/L (limited data)
<5 mg/L
<5 to 10 mg/L
Following initial operation of the system,
vents were installed to reduce a vapor
accumulation that resulted from biodeg-
radation of the guar (biopolymer) used in
trench construction. Analysis of influent
and effluent ground-water samples
indicates that the F&G system is remov-
ing all target contaminants of concern to
below cleanup standards, and in most
cases to below detection limits. Accord-
ingly, the record of decision for this site
has been amended to establish this
technology as the permanent ground-
water remedy. For more information,
contact Annie Godfrey (EPA/Region 4) at
404-562-8919 or e-mail godfrey.annie
@ epa.gov, Karl Hoenke (Chevron
Environmental Management Company) at
(925) 842-9259 or e-mail
khoe@chevron.com, or Dean Williamson
(CH2M Hill) at 352-335-7991 or e-mail
dwilliam@ch2m.com.
Iron Reactive Barrier Used at
Rocky Flats Site
by Thomas Holdsworth, U.S. EPA/
National Risk Management
Research Laboratory
The U.S. EPA began working with the
U.S. Department of Energy (DOE) in 1995
to characterize a contaminated ground-
water plume at DOE's Rocky Flats site
outside Denver, CO. DOE is working to
achieve closure of the Rocky Flats site by
2006, and considers remediation of this
plume a crucial element of site closure.
Based on the results of site
characterization and ongoing
commitment to utilize innovative
treatment
technologies, DOE
decided to
rerriediate, the '
contaminated
ground water
through use of a
passive barrier. This
type of barrier
system requires no
operational energy
and minimal
maintenance, which
results in a
substantial cost
savings over use of
an alternative pump
and treat system.
Performance
assessment of the
barrier through
EPA's Superfund Innovative Technology
Evaluation (SITE) Program indicates that
the barrier system is removing
approximately 99% of the plume's
primary contaminants.
Ground-water contamination in this
area—known as the mound site plume—
originated from a former waste drum
storage area used by DOE hi the 1950s.
Consisting of shallow ground water with
a flow rate of 0.5 to 2.0 gallons per
minute, the plume horizontally extends
approximately 220 feet. Its primary
contaminants are uranium and volatile
organic compounds (VOCs), including
carbon tetrachloride, tetrachloroethene,
trichioroethene, and vinyl chloride.
Following excavation and removal of the
contamination source in 1997, the
passive barrier (designed by EnviroMetal
Technologies, Inc.) was installed in the
summer of 1998.
This barrier system begins with the
downgrade-side collection of ground
water in a subsurface hydraulic barrier
(French drain) lined with high-density
polyethylene. The drain is located in the
unconfined aquifer at depths ranging
from 8 to 15 feet below ground surface.
Ground water is diverted through the
drain to piping that transfers it by gravity
to the reactive media treatment system.
The system consists of two 10-foot (wide)
by 5-foot (deep) cylindrical reactors, each
of which contains 337 cubic feet of
granular, reactive (zero-valent) iron. To
provide a ground-water flow rate of 1
gallon per minute over a duration of 20
hours in each reactor, the reactors were
sized accordingly and installed in series
below surface grade. By treating ground
water sequentially in both reactors, VOCs
are dechlorinated to nonchlorinated
hydrocarbons, and uranium in the
oxidized state (U6+) is converted to
uranium in the reduced state (U4*) and
precipitated. Following treatment, ground
water exits the barrier system directly
through surface water that flows to
retention ponds.
EPA and DOE have monitored the
influent and effluent of this barrier system
on a quarterly basis since September
1998. Table 3 provides the average
results of ground-water sampling con-
ducted through June 2000.
In addition, water samples in 1-foot
increments throughout the reactive media
have been collected since project start-up
[continued on page 4]
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