TECH TRENDS
Ground Water Currents
A newsletter about soil, sediment, and ground-water characterization and remediation technologies
September 2002
Issue 2
Sediment Capping Pilot Study Conducted on Grasse River
r* rom July to October 2001, Alcoa Inc. studied
the potential for constructing a full-scale
subaqueous cap to isolate or reduce
polychlorinatedbiphenyl (PCB) concentrations
in sediments, water, and biota of the lower
Grasse River near Massena, NY. The pilot
study evaluated capping as a remedial
alternative for the river and provided
information on technical implementation,
potential short-term effects of construction, and
the cost of the cap. Various capping materials
were placed into a 750-foot stretch of the river
using different placement techniques. The study
found that a cap of acceptable uniformity,
thickness, and composition could be placed
without significant PCB entrainment from the
in-place sediments and without significant
impacts to water quality. Optimal results were
achieved at this site using a sand/topsoil
capping material applied with a clamshell
attached to a barge-mounted crane.
The study site consisted of 7 acres located in a
stretch of the river containing fine-grained
sediment. As a result of previous manufacturing
operations, PCB concentrations of up to 11.5
mg/kg were identified in surface sediment.
Capping materials were tested in four cells
during two project phases.
The first phase was designed to assess a variety
of capping materials and application methods
in a cell comprising five subcells ranging in
size from 19,000 to 38,000 sq ft. Using one to
three application lifts, four different capping
materials were evaluated at thicknesses of 0.75-
1.0 ft: a sand/topsoil (1:1 ratio) mixture,
granular bentonite, a sand/soil/bentonite slurry,
and AquaBlok™ (a commercial bentonite clay/
gravel composite).
Sand/topsoil and AquaBlok materials were
installed using a crane-mounted clamshell that
released the materials at various water depths.
To accomplish this, an equipment barge carrying
an 80-ton crane was outfitted with a 2.5-yd
mechanical clamshell bucket. Capping materials
were prepared at an on-shore staging area and
placed on a separate barge. Accurate horizontal
control of the bucket, a key element of successful
cap placement, was achieved using global
positioning system software (WINOPS™) and
physical markers on the equipment. Apneumatic
broadcasting technique was used to apply the
granular bentonite material, and a subsurface
tremie method was employed to inject the sand/
soil/bentonite slurry. All capping work was
cordoned off using a single silt curtain that
extended from the water surface to within a few
feet of the river bottom.
The second phase of pilot testing was conducted
in three 50,000-sq-ft cells. Evaluation criteria
included cap coverage characteristics,
entrainment of contaminants into the cap, water
quality impacts, placement rates, logistic issues,
and costs. A cap thickness of 1 ft was targeted
for two of the cells, while a thickness of 2 ft was
targeted for the third. With the exception of
AquaBlok (on which tests were completed
during the first phase) capping materials and
techniques tested in each of the three cells were
similar to those tested during the first phase.
Approximately 900 water samples and 490
sediment samples were collected and analyzed
during the study. The results show that over 95%
of the PCB concentrations in core samples taken
through the pilot cell cap materials were at non-
detect levels (below 0.1 mg/kg). Mixing of the
[continued on page 2]
Contents
Sediment Capping
Pilot Study Conducted
on Grasse River page 1
Food-Grade Oil
Injections Used to
Stimulate Reductive
Dechlorination page 2
In-Situ Chemical
Oxidation Pilot
Conducted for CVOCs
in Fractured Bedrock page 3
Electrochemical
Remediation
Technologies Remove
Mercury in Soil page 5
New Resources for
Contaminated
Sediment Management page 6
Technical Training
Seminars Available
On-Line
As part of its continued efforts to
provide technical training
webcasts, the U.S. EPA Technol-
ogy Innovation Office (TIO)
recently held a "Perchlorate
Update" workshop online. This
workshop disseminated current
information on contamination
problems posed by perch lorate.
To view the perchlorate workshop
materials or participate in future
webcast training, visit TIO's CLU-
IN website at www.clu-in.org.
Recycled/Recyclable
I Printed with Soy-Canola Ink on paper that
contains at least 50% recycled fiber
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[continued from page 1]
cap material with underlying sediment, where
it did occur, generally was limited to the lowest
1-2 inches of capping material. PCB
concentrations in water downstream of the
cells were below the analytical detection limit
(50 ng/L) (Figure 1).
Water quality monitoring during cap placement
indicated that no significant releases of PCBs
(as shown in Figure 1), total suspended solids,
or turbidity occurred during the project.
Additionally, post-capping analyses of the
site's benthic community showed evidence of
recolonization of the capped area within three
weeks of the capping completion. Post-
capping monitoring of the bathymetry (river-
bottom profile) after the first winter shows the
cap thickness remains stable.
Unit costs to implement the capping activities
(excluding mobilization, silt curtains, design,
monitoring, and management) averaged $2.15/
sq ft for the 1-ft cap and $3.10/sq ft for the 2-
ft cap. Total costs for the study are expected
to range from $3.5 million to $4.0 million.
Project monitoring will continue at the Grasse
River study site throughout 2002.
Contributed by Larry McShea (Alcoa Inc.)
at 724-337-5458 or
larry.mcshea @alcoa. com; Mary Logan
(U.S. EPA/Region 2) at 212-637-4321 or
losan. mary@ epa. sov; and Joseph Mihm
(Camp Dresser & McKee) at 315-769-7011
or mihmie @ cdm. com
Food-Grade Oil Injections Used to Stimulate
Reductive Dechlorination
The U.S. Air Force Center for
Environmental Excellence (AFCEE) and Air
Education and Training Command (AETC)
teamed with Altus Air Force Base (AFB) to
sponsor field studies on the use of vegetable
oil for stimulating in-situ anaerobic
bioremediation of chlorinated solvents. Full-
scale applications at several military sites
indicate that the technology can reduce
contaminant concentrations at a lower cost
than conventional methods such as pump
and treat. Most recently, results from a pilot
study at Altus AFB, OK, showed over 90%
reduction in trichloroethene (TCE)
concentrations within eight months.
The process blends food-grade vegetable oil
and surfactants in a high-speed mixer to
generate an oil-in-water emulsion with a
small droplet size that can be distributed
easily throughout the subsurface. The
emulsion is injected through permanent
wells or temporary direct-push points. Water
is subsequently injected to distribute and
immobilize the oil. The optimum oil droplet
size and surfactant characteristics for each
site are determined through laboratory
testing.
Historical solvent releases of degreasing
agents at Altus AFB resulted in a 5,000-ft-
long chlorinated solvent plume with TCE
detection
limit
(50 ng/L)
concentrations reaching 78,000 |J,g/L in the
source area. Geology at the site consists
of reddish-brown, moderately plastic,
sandy clay to a depth of roughly 15 ft,
underlain by fractured clayey shale with
occasional gypsum layers. The depth to
ground water is 8-10 ft below ground
surface (bgs). Most ground-water flow and
contaminant transport appears to occur
through a series of weathered shale
fractures located immediately beneath the
surficial clay and within a thick gypsum
layer approximately 35 ft below grade.
Field observations suggest a ground-water
velocity approaching 100 ft/yr.
The pilot study is evaluating the use of
vegetable oil as a low-cost carbon source
for controlling chlorinated solvent
migration through enhanced anaerobic
bioremediation. A line of six permanent 2-
inch PVC wells spaced 5 ft apart was
installed perpendicular to ground-water
flow approximately 250 ft downgradient
from the source area. Over a 4-day period
in December 2001, a mixture of emulsified
soybean oil, yeast extract, and lactate was
injected through each well to form a 30-ft-
wide vegetable oil barrier that would
stimulate reductive dehalogenation.
Each injection was designed to treat a 6-
ft-diameter area that would provide a small
overlap between adjacent injection points.
To achieve maximum distribution of the
treatment mixture in the upper weathered
fracture zone, the wells were screened from
8 to 18 ft bgs. The cost of installing the six
barrier wells and injecting the mixture was
$18,000, or $600/linear ft of barrier.
Monitoring of adjoining wells during the
injection process showed that the
[continued on page 3]
500 Feet
Upstream
Immediately
Outside Silt
Curtain
750 Feet
Downstream
*Pilot cell #1 (of first phase) is not illustrated.
**A value of 1/2 the detection limit (25 ng/L) was assigned to non-detect readings when calculating averages.
Figure 1. Capping studies on the Grasse
River showed minimal impact on surface
water quality.
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Figure 2. TCE concentrations at the
Altus AFB pilot study site dropped
immediately after injection of vegetable
oil.
[continued from page 2]
emulsified oil was distributed to a distance of
more than 20 ft from the injection points. TCE
concentrations dropped immediately after
injection due to dilution and/or sorption to
the oil. By August 2002, however, TCE and
ds-dichloroethene (DCE) had rebounded and
total ethenes had returned to a level exceeding
90% of the preinjection concentration. These
changes indicated that dilution/sorption no
longer was significant and that any reduction
in contaminant concentrations was due to
biodegradation.
Data obtained from one of the six injection
wells indicated that the TCE concentration
had declined from 1,300 \igfL to 98 \igfL
(Figure 2), with 64% of the original TCE and
DCE recovered as ethane. Similar TCE
reductions were identified in a monitor well
located 20 ft downgradient from the barrier,
where the concentration dropped from 1,660
|j,g/L to 20 |J,g/L. Concentrations of vinyl
chloride (an intermediate break-down
product) had increased over the 8-month
period, indicating that conversion of TCE to
ethane was incomplete. Additional monitoring
is underway to determine if the barrier width
should be increased to achieve complete
conversion of vinyl chloride to ethene.
Final results from the pilot test will be used to
evaluate potential application of edible oils
for full-scale remediation of ground water at
Altus AFB. This pilot, as well as previous
applications at Dover AFB and Edwards AFB,
demonstrate the potential for application of
this process in a flow-through barrier for
controlling chlorinated solvent migration.
Previous commercial applications suggest that
this technology also could be used to treat
source-area hot spots and to enhance natural
attenuation of contaminants. Laboratory
studies are planned to evaluate the use of this
approach for treatment of other pollutants,
including nitrate, perchlorate, chromium,
radionuclides, and acid mine drainage.
16OO -i
TCE
c/s-DCE
vinyl chloride
ethene + ethane
Pre-lnjection
1 Day After
Injection
4 Months After
Injection
8 Months After
Injection
This project is part of the AFCEE Enhanced
Bioremediation Initiative, which is
investigating other low-cost substrates such
as molasses, direct hydrogen sparging, and
bark mulch in a trench application [see the
July 2002 issue of Technology News and
Trends]. The U.S. Air Force, Navy, and Army
also are developing a joint Tri-Service
guidance manual to outline criteria for
selecting appropriate carbon substrates and
cost estimating tools in bioremediation
applications.
Contributed by Dr. Bob Borden (Solutions-
IBS) at 919-873-1060 or
rborden @ solutions-ies. com; Jim Gonzales
(HQ/AFCEE) at 210-536-4324 or
james.gonzales@brooks.af.mil; Steven
Daneke (HQ/AETC) at 210-652-3302 or
steven.daneke@randolph.af.mil; and Dr.
Michael Lee (Terra Systems, Inc.) at 302-
798-9553 or mlee @ terrasvstems. net
In-Situ Chemical Oxidation Pilot Conducted for CVOCs
in Fractured Bedrock
A recent pilot program undertaken by the
Naval Facilities Engineering Command at
the South Weymouth Naval Air Station
(NAS), MA, illustrates the challenges posed
by contaminants in fractured-bedrock
aquifers. In-situ chemical oxidation (ISCO)
based on Fenton's chemistry was performed
to assess the technology's effectiveness in
destroying chlorinated volatile organic
compounds (CVOCs) in this type of setting.
Although initial post-injection sampling
showed overall contaminant reductions in
ground water, subsequent sampling indicated
significant contaminant rebound.
From the 1940s through the 1990s, the
2,800-sq-mi NAS study site was used for
vehicle maintenance. As a result, shallow
subsurface CVOC releases became mixed
with waste oil leaking from an underground
storage tank. The site is underlain by
approximately 6 m of silty sands, beneath
which exists a fractured granite formation.
The water table is located approximately 3
mbelow ground surface (bgs). Ground water
flows horizontally in both the overburden
and bedrock, which are in direct hydraulic
connection.
Slug tests and packer pressure tests in the
bedrock treatment zone indicated a hydraulic
conductivity ranging from 4.3 x 10"5 to 2.6
x 10"4 cm/s. An average fracture aperture of
156-349 mm was measured, and an effective
porosity of 1.03 x 10'3 to 2.86 x 10'3
calculated. Based on these parameters, the
bedrock treatment zone was estimated to
contain approximately 36,000 liters of water
and to require 88-243 days to flush one
fracture volume through the zone.
[continued on page 4]
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[continued from page 3]
The 90-m CVOC plume, ranging in width
from 20 to 45 m, extended 30 m below the
top of the fractured bedrock (35-40 m bgs)
prior to ISCO treatment. Baseline sampling
found that total CVOC concentrations in two
wells exceeded 1,000 mg/L. In the remaining
43 pilot wells, 14 indicated concentrations of
100-1,000 mg/L and 29 indicated less than 100
mg/L. The cross-sectional distribution of
C VOCs with depth does not provide evidence
of DNAPL pools. Based on the persistence
and pattern of CVOC rebound modeled over
time, however, DNAPL may exist in poorly
connected, soil-clogged fractures near the
overburden-bedrock interface.
The ISCO process employed at the NAS
involved simultaneous injection of hydrogen
peroxide and a ferrous sulfate catalyst into the
overburden and fractured bedrock zones. The
first phase of injections, which occurred in
October 2000, employed 48 injectors spaced
at 3 m intervals. Of these, 20 were screened
across the saturated portion of the overburden
and 28 were screened within the fractured
bedrock. Prior to the second (final) injection
phase in March 2001, three additional bedrock
injectors were installed to improve fracture
accessibility. A total of 9,233 liters of peroxide
and 28,174 liters of catalyst was injected.
Pilot results indicate that CVOC
concentrations in ground water within the
bedrock were depressed during and
immediately following each phase of injection
but rebounded over time at many of the
observation points. Figure 3 presents data from
two representative observation points. A well
outside the treatment zone shows the peroxide
and catalyst (represented by iron)
equilibriating, thereby allowing the CVOCs
and BTEX to rebound. A well in the center of
the treatment zone shows the continued
persistence of catalyst, which may be
artificially depressing the CVOC and BTEX
concentrations.
Analysis of monitoring data suggests that a
significant amount of dilution occurred due
to the addition of peroxide and catalyst (iron).
Increased concentrations of dissolved oxygen,
as indirect measures of CVOC breakdown
and/or the presence of hydrogen peroxide,
were observed in 77% of the monitoring wells.
Data suggested that 9-12 months were needed
for the bedrock system to flush the injected
fluids and for CVOC concentrations to re-
equilibrate.
Although limited success of ISCO treatment
was achieved at the South Weymouth NAS,
the pilot refined delineation of the residual
contamination source, improved unders-
tanding about the interconnectivity of the
bedrock fractures, and better defined the
applications and limitations of ISCO treatment
in a fractured-bedrock setting. To more fully
characterize the current aquifer conditions,
efforts are underway to further assess the
overburden-bedrock interface, the potential
DNAPL source areas, and the treatability
parameters for alternate remedies. Potential
technologies for this site include the injection
of alternate oxidants and stimulated anaerobic
microbial degradation.
Contributed by Mark Krivansky (Naval
Facilities Engineering Command) at 610-
595-0567 or
krivanskyme @ efane. navfac. navy, mil; Mark
Kauffman (ENSR International) at 978-
589-3000 or mkauffman @ ensr. com; Bill
Brandon (U.S. EPA/Regionl) at 617-918-
1391 or brandon.bill@epa.sov; and Patty
Marajh-Whittemore (U.S. EPA/Region 1) at
617-918-1382 or
whittemore. vattv @ eva. sov
Well Located 2 Meters Outside Treatment Zone
1000
100
1 101
o
o
1 •
0.1
Saseline Sampling
October 2000
Treatment
March 2001
Treatment
1000
Well Located in Approximate Center of Treatment Zone
-*- total CVOCs (|ig/L)
-6- total BTEX (jig/L)
— total iron (ng/L)
• peroxide (mg/L)
en
c
O
"5
o
O
Figure 3. While contaminant reductions
significant rebound occurred in others.
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Electrochemical Remediation Technologies Remove Mercury in Soil
.Pilot- and full-scale in-situ remediation
projects were conducted at several European
sites to evaluate the use of innovative
electrochemical remediation technologies
(known as "ECRTs") forremoval of mercury
and other metals from soil. Based on these
project results and recent bench-scale testing,
the U.S. Department of Energy (DOE) is
considering an ECRTs field pilot for removal
of mercury and other heavy metals at the
National Security Complex (Y-12) near Oak
Ridge, IN. Cost reduction is the maj or driver
for DOE to seek alternative cleanup
technologies such as these. ECRTs require
low levels of electrical energy input
compared to other electrical methods such
as traditional electrokinetics, joule heating,
and vitrification. In addition, ECRTs
generally are effective within months, instead
of years, and can be performed in-situ or ex-
situ.
ECRTs involve the passage of low-voltage/
amperage AC/DC current between an
electrode pair to create metallic complexes.
The ion complexes, as well as ionic metals,
are mobilized via the electrokinetic gradient
to both the anode and cathode for deposition.
These deposits then can be removed and
recycled. In contrast to electrokinetics,
ECRTs electrically polarize the soil to
generate reduction-oxidation (redox)
reactions at the pore scale, creating mobile
species of the target contaminants that
migrate to the electrodes. Field remediation
projects suggest that the overall reaction rates
of the electrochemical process are inversely
proportional to grain size of the soil or
sediment undergoing treatment.
These technologies were demonstrated at the
Union Canal in Scotland, where an average
total mercury (elemental and methyl
mercury) concentration of 243 mg/kg was
present in the silt of a 1.1 -m-deep, brackish-
water canal. Over a 26-day period, 220 cubic
meters of contaminated silt were treated.
Approximately 5.6 kW of electrical power
was applied to two electrode pairs placed
within the silt at positions parallel to the canal
banks. After 12 days of treatment, the average
total mercury concentration dropped to 119
mg/kg. The target goal (20 mg/kg) was
exceeded by the end of the demonstration, at
which time the average mercury concentration
was 6.5 mg/kg. A total of 76 kg (168 Ibs) of
metal deposits, primarily consisting of
mercury, accumulated on the electrodes.
Bench-scale testing of mercury-contaminated
soil from DOE's Y-12 facility corroborated
previous ECRTs field results. The test was
conducted on homogenized soil having an
average total mercury concentration of 252
mg/kg. Chemical analysis of the soil showed
it contained up to 12,000 mg/kg of iron, which
created conditions for high electrical
conductivity and allowed for laboratory
simulation of the ECRTs process.
After 741 hours of testing on the Y-12 soil,
the total mercury concentration in soil near
the anode increased to more than 530 mg/kg
(>120% relative to baseline). In soil near the
cathode, the total mercury concentration
decreased by approximately 60%. Post-test
chemical analysis of the electrodes themselves
indicated that the anode accumulated about
four times more total mercury than the
cathode. The combined chemical data from
soil and electrode analyses indicated that
mercury was migrating and depositing at both
electrodes. This generation and migration of
both positive and negative chemical species
to their respective electrodes distinguishes
ECRTs from classical electrokinetics
techniques.
Preliminary engineering cost estimates for
ECRTs range from $135/yd3 (for volumes of
3,000 yd3) to $42/yd3 (for volumes exceeding
100,000 yd3). An ECRTs demonstration also
is being conducted by the U.S. Army Corps
of Engineers, the U.S. EPA Great Lakes
National Program Office, and the Minnesota
Pollution Control Agency to evaluate its use
in removing polycyclic aromatic
hydrocarbons (PAHs) in fresh-water
sediments of Lake Superior. In addition,
the Washington State Department of
Ecology and King County, WA, are
cooperating with the U.S. EPA in a
Superfund Innovative Technology
Evaluation (SITE) Program demonstration
of the technologies' ability to reduce
concentrations of PAHs, mercury, and
phenols in marine sediments.
Contributed by John Michael Japp
(DOE/Oak Ridge Operations Office) at
865-241-6344 or jappjm @ oro. doe, sov;
Karen Cohen (DOE/National Energy
Technology Laboratory) at 412-386-
6667 or cohen@netl.doe.sov; Folk
Doering (P2-Soil Remediation, Inc.);
and Joe lovenitti (Weiss Associates/The
Providence Group/ADA Technologies,
Inc.) at 510-450-6141 orjli@weiss.com
Contact Us
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Phone: 703-603-7199
Fax: 703-603-9135
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Technology
News and Trends
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-02-004
September 2002
Issue No. 2
United States
Environmental Protection Agency
National Service Center for Environmental Publications
P.O. Box 42419
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EPA is publishing this newsletter as a means of disseminating useful information regarding innouatiue and
alternative treatment techniques and technologies. The Agency does not endorse specific technology vendors.
New Resources for Contaminated Sediment Management
Sediment experts representing a variety of research organizations recently collaborated in developing an 88-page white paper,
Critical Issues in Contaminated Sediment Management. The white paper addresses a range of technical issues:
Assessment of monitored natural recovery
Monitoring of remedial effectiveness
Conceptual site models
Contaminant bioavailability
I Characterization of the spatial extent of contamination
In-situ bioaccumulation tests
Sediment toxicity testing
Ecological assessment tools
Field screening or rapid sediment characterization tools
The white paper was published by the Marine Environmental Support Office of the U.S. Navy (publication number MESO-02-TM-
01) and is available on the SedWebSM bulletin board at www.sediments.org/sedmgt.html. Other sediment-related information, including
on-line discussions and audio web lectures, can be found on SedWeb as a service of the Hazardous Substance Research Centers/
South & Southwest.
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