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welcomes readers' comments and contribu-
tions, and new subscriptions. Address
correspondence to:
Ground Water Currents
8601 Georgia Avenue, Suite 500
SiIver_Spring,MaryJand_2Qai 0 _z_^
Fax:301-589-8487 ~ ~= ~~"
Engineering Service Center) at 805-982-
1660 or E-mail yehsl@nfesc.navy.mil, or
Mark Hasegawa (Surbec Environmental,
LLC) at 405-364-9726 or E-mail
markhase@aol.com.
Training on Permeable
Reactive Barriers
In Situ Permeable Reactive Barriers:
Application and Deployment training
courses are being offered in each of EPA's
regional office areas to assist professionals
in the regulatory community in overseeing
the design, implementation, and monitor-
ing of ground water remedies involving
permeable reactive barriers. The U.S. EPA,
Interstate Technology Regulatory Coopera-
tion, and Remediation Technologies
Development Forum jointly developed the
course to meet the demand for more
information on the effectiveness, cost, and
general use of permeable reactive barriers.
Since June 1999, the training course has
"
and Philadelphia, PA. Future locations and
dates for the course are:
• Dallas, TX, on. November 16-17, 1999
• Atlanta, GA, on February 8-9, 2000
• San Francisco, CA, on March 21-22,
2000
• New York, NY, on May 2-3, 2000
• Denver, CO, on June 13-14, 2000
• Chicago, EL, on July 25-26, 2000, and
• Kansas City, MO, on September 12-13,
2000.
Participants may register for the course via
the Internet at http://www.trainex.org/prb or
by contacting the Southern States Energy
Board at 770-242-7712.
Conference on Present and
FutureTechnoIogy
Developments
The U.S. EPA will sponsor the
conference Innovative Clean-Up
Approaches: Investments in
Technology Development, Results, &
Outlook for the Future at the Indian
Lakes Resort in Bloomingdale, IL,
November 2-4,1999. Stakeholders in
Hazardous waste site remediation
projects, including EPA's partners from
other government agencies, academia,
and the private sector, will have an
opportunity to share the latest
information on technology
development, demonstration, and
commercialization. Participants also
will evaluate the success of past
efforts and discuss future research
and information needs. Workshops
will be available to provide information
on the SITE Program, Brownfields
Program, funding sources, and
electronic information resources. On-
line program information, including an
updated conference agenda, is
available on the Internet at
www.epa.gov/ttbnrmrl.
United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-99-006
September 1999
Issue No. 33
Vv&ter Treatment
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Figure 2. Relative Rates of Reaction: Contaminants Tested for HPO
10.0
1 «
I
1
Rslative F
ra
0.9
Fastest
In carbon tetrachloride
oTCE
| pentachlorophenol
* methyl-tertiary butyl ether
?
i ethylbenzene
f polychlorinated biphenyl
| napthalene
* perchloroethylene
I • NllBM 1 Ullmlllllllllll mlllimmBfflp
Results
• Every chemical tested has
been destroyed by hydrous
pyrolysis/oxidation to below
maximum contaminant levels
Carbon dioxide and chloride
ion are the observed products
-Slowest * dimethyl nitrose amine
Following two years of treatment, 77,111
kilograms of creosote have been oxidized in
place.
Several techniques are used to monitor the
underground movement of steam and rates
of contaminant removal. Electrical resis-
tance tomography is used to provide daily
pictures of the steam front progress and the
heated /.ones, thus ensuring that all soil is
treated. Thermal measurements also are
used. In order to verify the progress and
extent of hydrous pyrolysis/oxidation,
Noble-gas tracers were used to track water
movement and verify that chemical
reactions are occurring as expected. To
evaluate the progress of chemical destruc-
tion, high-temperature systems capable of
delivering a pressurized, isolated fluid
stream to the surface were developed to
allow for in-line analysis.
Researchers from the Lawrence Livermore
National Laboratory (LLNL) responsible for
development of the process estimate that
large-scale cleanups with hydrous pyrolysis/
oxidation at other sites could cost as little as
$33 per cubic meter. For more information,
contact Roger Aines (LLNL) at 925-423-
7184 or E-mail aines I @llnl.gov, or Robin
New-mark (LLNL) at 925-423-3644 or E--
mail newmarkl@llnl.gov.
Surfactant-Enhanced
Subsurface Hemediation
to Remove DNAPL
by Laura Yea, U.S.Navy/NFESC,
and Mark Hasegawa, Surbec
Environmental, LLC
The U.S. Navy is conducting a pilot-scale
surfactant enhanced subsurface remediation
(SESR) project at Alameda Point (former
Naval Air Station) located in Alameda, C A.
The SESR system is designed to remove
trapped dense non-aqueous phase liquids
(DNAPL), primarily consisting of
trichloroethane, trichloroethylene,
dichloroethylene, and dichloroethane, from
the soil matrix. This
project is the first to
demonstrate the
recycling and reuse
of a dual surfactant or
cosurfactant system.
Injection recovery
wells were installed
and a tracer test was
conducted prior to
the SESR demonstra-
tion to confirm
hydraulic capture of
fluids, and to
quantify the DNAPL mass existing within
the 20- by 20-foot test area. The surfactant
solution, which consists of 5% (by weight)
Dowfax 8390,2% AMA (food-grade
biodegradable surfactants), 3% sodium
chloride, and 1 % calcium chloride, is
flushed through the aquifer to enhance
recovery of DNAPLS.
Recovered ground water is pumped through
a liquid-liquid extraction unit where the
NAPL constituents are removed from
solution. The remaining surfactant is
concentrated using physical filtration
(micellar enhanced ultrafiltration) and then
reinjected into the system. Reuse of the
surfactant provides a significant reduction
in project costs. Figure 3 provides an
overview of the process.
The goal of the project is to remove 95% of
the trapped DNAPL from the test area
within 10 days. Preliminary mass removal
estimates show that up to 80 gallons of
DNAPL was recovered during the test. Post
test soil coring results indicate no detect-
able DNAPL remaining in the flushed zone.
Final project results are expected to be
available in October 1999. ;
Additional soil coring will be conducted in
conjunction with post-test partitioning
tracer tests to confirm the mass of DNAPL
removed. For more information, contact
Laura Yea (U.S. Navy/Naval Facilities
Figure 3. Surfactant-Enhanced Subsurface Remediation
Flow
'Foam
Air Stripping/
Foam Fractionatiqn/
Activated Carbon
Recovery Well
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subsurface (higher permeability lenses or
macropores).
Based on these results, USAGE researchers
identified three scenarios that can result
from application of MPE technology:
(1) At sites with excessively high
permeability and low air-entry
pressures (capillary fringe thickness
less than 25 centimeters), MPE wells
with slurp tubes will tend to flood
with water, very little air flow will be
induced, and efficiency of the process
_will be compromised (Figure 1 , left) .
~"
E-mail rbaker@ensr.com or
dgroher@ensr.com; or David Becker
(USAGE Toxic and Radioactive Waste
Center of Expertise) at 402-697-2655, E-
mail dave.j.becker@usace.army.mil.
Hydrolysis Pyrolysis and
Oxidation Used at a
Creosote Site
by Roger Aines, Ph.D., and
where air-entry pressures are low
(capillary fringe thickness of 25-250
centimeters), MPE should be able to
enhance air flow significantly and
cost-effectively (Figure 1, center).
(3) At sites with lower permeability soils
with high air-entry pressures (capil-
lary fringe thickness greater than 250
centimeters), MPE will not be capable
of dewatering the soil. As a result, air
flow will be limited to a few preferred
pathways, while the bulk of the soil
will remain saturated (Figure 1, right).
The USAGE has incorporated these findings
in a comprehensive MPE Engineer Manual
(EM 1110-1-4010) that will be available
this Fall on the Internet (http://www.usace.
army.mil/inet/usace-docs/). For more
information, contact Ralph Baker or Dan
Groher (ENSR Corp.) at 978-635-9500,
Lawrence Livermore National
Laboratory
Since 1997, a new remediation technology
involving in situ thermal oxidation
through hydrous pyrolysis has removed
solvent and petroleum contaminants hi
ground water and soil at the Visalia Pole
Yard in Visalia, CA. This process effec-
tively converts certain contaminants to
benign products such as carbon dioxide,
water, and chloride ions, and mobilizes
other contaminants. By eliminating the
need for long-term use of expensive
treatment facilities, the process is proving
to reduce cleanup costs at Visalia signifi-
cantly. Original estimates that cleanup of
this site would take approximately 120
years (using traditional pump and treat
technology with enhanced
bioremediation) have been reduced to
-enly~feuriyears4hr©ugb
Figure 1. Hypothetical Scenarios during MPE
x'"—Piezometric Surface
pyrolysis/oxidation (HPO) and other
innovative technologies.
Hydrous pyrolysis/oxidation is based on the
principles used in dynamic underground
stripping. (See the June 1998 issue of
Ground Water Currents for a related discus-
sion.) At temperatures achieved by steam
injection, organic compounds will oxidize
readily over periods of days to weeks. By
introducing both heat and oxygen, this
process effectively has destroyed all petro-
leum and solvent contaminants that have
teen tested in the laboratory (Figure 2). The
*
oxidatiorTof contaminants *at steam tempera-"
tares is extremely rapid (less than one week
for trichloroethene (TCE) and two weeks for
naphthalene) if sufficient oxygen is present.
With dynamic underground stripping, the
contaminants are vaporized and vacuumed
out of the ground, leaving them to be
destroyed elsewhere. In HPO, the dense,
nonaqueous-phase liquids and dissolved
contaminants are destroyed in place without
surface treatment, thereby improving the rate
and efficiency of remediation by rendering
the hazardous materials benign by a com-
pletely in situ process. Because the
subsurface is heated during the process, HPO
takes advantage of the large increase in mass
transfer rates (such as increased diffusion out
of silty sediments) making contaminants
more available for destruction.
At the Visalia Pole Yard, dynamic
underground, stripping combined with
hydrous pyrolysis/oxidation uses
simultaneous injection of steam and oxygen
to build a heated, oxygenated zone in the
subsurface. When injection is halted after the
target volume reaches steam temperature
(typically 2-4 weeks), the steam condenses
and contaminated ground water retains to the
heated zone, mixing with condensate and
oxygen to destroy any dissolved
contaminants. Non-aqueous phase liquid
contaminants such as creosote and TCE are
mobilized and recovered by pumping the
treatment zone after steam condensation.
The oxidation of dissolved contaminants at
steam temperatures generally occurs hi less
than four days if sufficient oxygen is present.
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United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-99-006
September 1999
Issue No. 33
cvEPA Ground Water Currants
reatment
CONTENTS
Minimal Desaturation
Found during Multi-
Phase Extraction of
Low Permeability
Soils Pg. 1
Hydrolysis Pyrolysis
and Oxidation Used
at a Creosote Site Pg. 2
Surfactant-Enhanced
Subsurface
Remediation to
Remove DNAPL Pg. 3
Training on Permeable
Reactive Barriers Pg. 4
Conference on 31
Technology Development
About this Issue
This issue highlights
enhanced techniques for
applying innovative
tcchnnologies in the
remediation of contaminated
ground water.
Minimal Desaturation
Found during Multi-Phase
Extraction of Low
Permeability Soils
by Ralph Baker and Dan Groher,
ENSR Corp., and David Becker,
U.S. Army Corps of Engineers
Multi-phase extraction (MPE) typically is
used to simultaneously remediate soil and
ground water, improve the recovery of
ground water from moderately low
permeability soils, and/or improve the
performance of soil vapor extraction by
controlling water table upwelling and
reducing soil moisture saturation. As part
of an effort to develop guidance for
implementation of MPE technology, the
U.S. Army Corps of Engineers (USAGE)
has conducted field studies on soil
desaturation at sites with chlorinated
hydrocarbons in soil and ground water.
Although MPE generally is viewed as an
enhancement of soil vapor extraction
capable of dewatering saturated soils,
results of the studies indicate that MPE
did not dewater low permeability soils
significantly. Under certain conditions,
however, MPE was found to remove large
amounts of contaminant mass in low
permeability soils.
The effectiveness of MPE was evaluated
from 1996 to 1998 at three CERCLA pilot
test sites, two of which are manufacturing
facilities located in geomorphologically
dissimilar settings at an Army ammunition
plant (AAP) in the Midwest. The third test
site is a former chemical waste reclama-
tion facility in the Northeast.
Tests at each site used a slurp tube
positioned within the screened interval of
a single extraction well. Vapor and liquid
were suctioned via the slurp tube to an
aboveground equipment/treatment systqm.
Extraction rates of vapor and liquid were
measured downstream of the vapor-liquid
separator. Three to five neutron probe
access tubes in the vicinity of the extrac-
tion well and a neutron moisture meter
were used to profile changes in the liquid
content of the formation surrounding the
access tubes. Analyses of intact soil cores
from the MPE target zone provided data
on moisture characteristics used to
indicate the degree to which an initially
saturated soil sample would be dewatered
at equilibrium with a given level of
applied vacuum.
Significant contaminant mass was
removed during these tests. At one of the
AAP sites, 379 kilograms of total volatile
organic compounds (VOCs) were removed
as vapor, and 17 kilograms as liquid. At
the second AAP site, 70 kilograms of VQCs
were removed as vapor and 0.45 kilograms
as liquid. The vacuum influence varied
spatially to a great extent. Neutron
moisture profiles measured at each of these
sites exhibited small differences in liquid
content before versus after MPE. For
example, at one of the AAP sites, the silty
clay soils had initial moisture contents (by
weight) that ranged from 33 to 36 percent,
depending on depth. Over the course of
the 7-day pilot test, during which vacuums
of 40-61 centimeters of mercury were
applied, moisture contents measured only
1.5 meters from the extraction well
changed by less than 1 percent. Thus, an
insignificant amount of dewatering
occurred during MPE, and what did occur
was limited only to portions of the
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