United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-00-003
May 2000
Issue No. 37
V-/EPA
CONTENTS
Six-Phase Heating and
Radio Frequency
Heating Used at
Fort Wainwright pagel
Expansive Cover Installed
by DOE to Contain
Mixed Wastes in
Eastern Utah page 2
Pneulog Technology
Used by Air Force to
Optimize SVE page 3
Joint Technical
Remediation
Seminars to be
Held in June page 4
The Applied Technologies
Newsletter for Superfund
Removals & Remedial
Actions & RCRA Corrective
Action
ABOUT THIS ISSUE
This issue highlights various
innovative technologies in use
to characterize or remediate
federal facility sites with soil
contamination.
TECH TRENDS
Six-Phase Heating and
Radio Frequency
Heating Used at Fort
Wainwright
by Therese Deardorf, U.S. Army
Corps of Engineers
A recent treatability study conducted by
the U.S. Army Corps of Engineers at Fort
Wainwright, AK, shows that radio
frequency heating and six-phase heating
can effectively enhance soil vapor
extraction/air sparging (SVE/AS) in cold
climates. In addition to quantifying the
extent to which soil heating can increase
volatilization and biodegradation rates
during SVE and AS, the study served as a
trial for determining the effectiveness of
different heating techniques and
identified the cost-effectiveness of soil
heating.
Three independent study sites were
established: an unheated SVE/AS area,
an SVE/AS area with radio frequency
heating, and an SVE/AS area with six-
phase heating. In situ monitoring sensors
to measure oxygen, pressure, soil
moisture, and temperature were installed
at each site, and data were recorded twice
daily by data loggers. Soil samples were
collected before heating, at the end of
moderate heating, and at the end of high-
temperature heating. Both radio
frequency heating and six-phase heating
systems were evaluated on the basis of
their capability to heat a column of soil
40 feet in diameter and 6-18 feet below
grade.
Both systems were found capable of
heating soils at this site to moderate
temperatures. During moderate radio
frequency heating, soil temperatures
reached 15-40°C. It is estimated that this
system is capable of heating a soil
column up to 60 feet in diameter under
full-scale application. The delivery of
radio frequency heat from a single
generator and splitter system to the four
antennae used in this study resulted in
non-uniform soil temperatures. More
uniform temperatures likely would be
achieved through the use of an
independent power control for each
antenna.
During moderate six-phase heating, soil
temperatures reached 20-25°C. It is
estimated that a soil column up to 85
feet in diameter could be heated under
full-scale application. High-temperature
six-phase heating resulted in soil
temperatures that varied with radial
distances from the heating electrodes.
Temperatures of 100°C were reached
within an 8- to 10-foot radial distance
from the electrodes, while they averaged
85°C (to a depth of 6-16 feet) within a
50-foot diameter soil column.
Analysis of the oxygen uptake data, soil
sampling, and SVE offgas samples
indicated that the SVE/AS technologies
used at this site were enhanced through
soil heating. At temperatures of 20-
30°C, biodegradation rates averaged 2.4
mg/kg/day, a 4- to 5-fold increase over
ambient rates at temperatures of less than
5°C. At the end of moderate heating, the
average concentrations of gasoline-
range organics in soil decreased by 55
percent in the radio frequency heating
area and by 63 percent in the six-phase
heating area. By the study's conclusion,
more than 70,000 pounds of volatile
organic compounds had been removed
by the SVE systems.
[continued on page 2]
Recycled/Recyclable
Printed with Soy/Canola Ink on paper that
contains at least 50% recycled fiber
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[continued from page 1]
Overall, this treatability study found that
soil heating is cost-effective when
remediating compounds with low
volatility and where biodegradation is
the primary treatment mechanism.
Additionally, six-phase heating was
found to be more cost-effective than radio
frequency heating in large areas due to its
lower equipment costs and ability to treat
a larger area at one time. For more
information, contact Therese Deardorf
(USAGE) at 907-384-2716 ore-mail
deardorf@richardson-emh2.army.mil, or
Mark Wallace (USAGE) at 907-753-5660
or e-mail wallace@richardson-
emh2.army.mil.
Expansive Cover
Installed by DOE to
Contain Nixed Wastes
in Eastern Utah
by Joel Berwick, U.S. Department
of Energy/Grand Junction Project
Office, Timothy Meiers, MACTEC-
ERS, andJody Waugh, Ph.D., Roy
F. Weston, Inc.
Originally built in 1942 to provide
vanadium for World War II, and later
modified to process uranium, the
Monticello mill in Utah produced
extensive deposits of radioactive tailings
until its closure in the early 1960s. Over
the past year, the U.S. Department of
Energy/Grand Junction Project Office
(DOE/GJPO), the State of Utah
Department of Environmental Quality,
and Region 8 of the U.S. Environmental
Protection Agency (EPA) have
collaborated in the construction of a
cover to contain 2.5 million cubic yards
of radioactive material removed from the
Monticello mill Superfund site.
The large, multilayered cover combines
fundamental ecological principles with
engineered barriers that are required
under existing regulatory guidelines.
Ground-water recharge is limited
naturally at Monticello, where thick loess
soils store precipitation until evaporation
and plant transpiration (evapo-
transpiration) seasonally return it to the
atmosphere, thereby maintaining
unsaturated conditions in the subsoil.
The cover design mimics and enhances
this natural water balance. A capillary
barrier underlying a thick soil "sponge"
enhances water storage and prevents
downward unsaturated flow. The cover
also is designed to control radon flux,
biointrusion, and erosion, and to protect
critical layer interfaces from frost.
Preliminary studies of natural analogs
suggest that cover performance may
improve over the 1000-year design life,
even with expected climatic change,
ecological succession, and pedogenesis.
The 0.5- by 1.0-mile cover consists of the
following distinct
layers, from bottom
to top as shown in
Figure 1:
• A 60-
centimeter
compacted soil
layer designed
to hold radon
flux below a 20
pCi nr2 s"1
regulatory
standard and to
satisfy the
saturated
hydraulic conductivity standard of
this layer consist of stockpiled
topsoil. Two rock admixtures are
located below: a cobble admixture
placed 30 centimeters above the sand
to prevent burrowing mammals from
disrupting the capillary break, and a
20-centimeter gravel admixture at the
surface to provide erosion protection.
Vegetation consisting of a mixture of
native shrubs, grasses, and forbs
planted over approximately 60
percent of the cover. Revegetation is
designed to emulate the structure,
function, diversity, and dynamics of
native plant communities in the area.
This mixture of native plants should
maximize evapotranspiration and
remain resilient given inevitable
fluctuations in the environment.
Figure 1. Cover Cross Section
Vegetation
Topsoil
Water storage and
frost-protection
barrier
Geomembrane
Tailings •
Capillary moisture barrier/drainage layer
Radon/infiltration barrier
(Not to scale)
Note: Rock cover (riprap)
on side slopes not shown
A required 60-mil high-density
polyethylene (HOPE) geomembrane
that serves as a water-infiltration
barrier.
A 36-centimeter layer of well-graded
sand that functions as a capillary
barrier and drains any leakage from
overlying soil layers to the perimeter
of the cover.
A geotextile composed of non-woven
geosynthetic that serves as a layer
separator during construction.
A 163 -centimeter fine-textured soil
sponge layer designed for frost
protection and to store all
precipitation, even during extreme
years. The upper 30 centimeters of
• A rock cover placed on clean-filled
side slopes with gradients of 5:1 and
10:1.
The DOE/GJPO is collaborating with
EPA/Region 8's Alternative Cover
Assessment Program (ACAP) and DOE's
Office of Science and Technology on a
suite of five-year studies on water balance
or evapotranspiration covers at
Monticello. This site is one of twelve
nationwide that ACAP is monitoring to
acquire the necessary field data for
revising and simplifying EPA guidance
on designing hazardous waste landfills.
[See the February 1999 issue of Tech
Trends for additional information on
ACAP.]
[continued on page 3]
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[continued from page 2]
The ACAP test at Monticello uses three
types of lysimeters.
• Eighteen small-weighing lysimeters
are filled to evaluate the water
balance of cover designs with
varying soil types and sponge layer
thicknesses overlying a capillary
barrier.
• Two large-drainage lysimeters (3
meters in diameter) are used to
monitor the water balance of physical
models of the cover. Tests in these
two types of lysimeters address the
range of soil materials and
compaction achieved in the cover.
• The third lysimeter is an integral part
of a 3-hectare facet of the actual
repository cover. Any unexpected
water drainage from the soil sponge
onto the underlying HDPE
geomembrane would be captured in a
buried gutter at the edge of the top
slope and channeled to a sump where
the volume and flow rate can be
measured. Equipment for measuring
soil water storage, water potential,
and runoff also will be installed for a
complete water balance monitoring
system. This repository lysimeter is
perhaps the largest surface cover
lysimeter in the United States.
The cover's monitoring system has
produced preliminary data indicating that
no release of radioactive or hazardous
waste to the surrounding soil and ground
water areas has occurred. Under DOE's
Long-Term Surveillance and
Maintenance Program, the Monticello
repository cell will be monitored
annually, and the cover and adjacent
areas will be assessed for damage and
erosion on a quarterly basis. Vegetation
on the cover, which will be protected by a
wildlife fence for a minimum of five
years, is expected to be fully established
within two to three years. In addition, a
nearby triple-lined pond with leak-
detection capability will collect drainage
from the tailings for 5-20 years.
For additional information, contact Tim
Meirs, MACTECH-ERS at 435-587-4061
or e-mail tmeirs@doejgpo.com.
Pneulog Technology
Used by Air Force to
Optimize SVE
by Jim Cummings, U.S. EPA/
Technology Innovation Office, and
Lloyd Stewart, Ph.D., Praxis
Environmental Tech., Inc.
The U.S. Air Force and the U.S. EPA's
Technology Innovation Office have
collaborated on the initial deployment of
a new tool to reduce long-term
operational costs and accelerate cleanup
through the optimization of soil vapor
extraction (SVE) systems in unsaturated
zones. This technology, known as
PneuLog™ uses in-well instrumentation
to measure air permeability and
contamination production continuously
along a well screen during vapor
extraction. This approach to testing
involves the definition of soil
heterogeneity in individual wells to
identify mass transfer constraints in the
vadosezone. Data from several wells
then are used to optimize a remedial
strategy and estimate operation times for
meeting closure requirements.
This technology also has been used for
initial site characterization, resulting in
the rapid deployment of an SVE system
that targets contaminant-producing soil
layers and minimizes wasteful collection
and treatment of clean soil gas. In
contrast, conventional SVE design and
optimization procedures typically rely on
empirical data because field mass transfer
constraints (which are capable of limiting
remediation) are not quantified. As a
result, conventional systems may be
overbuilt, inefficient, and expensive to
operate.
quantify vertical profiles of air
permeability. These data sets are coupled
with extraction tests and historical data to
produce a scientific basis for SVE
optimization. Test equipment consists of
downhole instrumentation attached to a
cable that is raised or lowered by a
motorized reel. Electrical leads connect
the flow and contaminant sensors to a
data acquisition system on the ground
surface, and a photoionization detector
(PID) provides a continuous reading of
total contamination along the well
screen. Soil air samples are collected for
gas chromatographic analysis to
determine compound-specific
concentrations and to calibrate the PID
readings. Associated above-ground
software displays the cumulative airflow
and total contaminant concentration as
functions of depth in real time.
Results from a typical pneumatic log
(Figure 2) performed in Sacramento, CA,
represent the type of information that
may be obtained from Pneulog testing.
At this site, the well was screened 12-32
feet below ground surface (bgs), and a
vacuum of 17 inches of water was applied
to the well. The resulting air extraction
rate was approximately 40 standard cubic
feet per minute (scfm). In Figure 2, a and
b illustrate the raw cumulative data, while
c and d indicate corresponding air
production and estimated contaminant
(trichloroethylene [TCE]) concentrations
within the production zones.
These results suggest that the
contaminants extend beyond the screen
interval and within low air production
zones (Figure 2d). In addition, two
significant air flow zones located at 12-
[continued on page 4]
The PneuLog
approach
incorporates short-
term soil vapor
extraction with
pneumatic well
logging to delineate
the horizontal and
vertical extent of
contaminants and to
0 n
5
10
J 15
a. 20
Q
25
30
35
(
Figure 2. PneuLog Data and Output
a i
I
1
S^
::
I
m
M
b »
/
V
X
' 1
LJ *
•\
m
-
m
IM
20 40 60 0 20 40 60
Cumulative Soil Vapor Cumulative TCE Cone.
Flow (scfm) (mg/m3)
C
^mmmmmmmmmS
L™.
•
|
1
d
i |
|
1
^^
r
0 5 10 15 0 20 40 60
Soil Vapor Production TCE Vapor
(scfm/ft) Concentration (mg/m3)
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[continued from page 3]
14 feet bgs and 16-21 feet bgs were
identified; these zones correspond to
coarse material (sandy gravel) observed
during drilling. Test data also indicate
that the highest contaminant
concentrations are located in the
unproductive silt and in the soils above
the top of the screen. Contaminants are
extracted from this well, therefore,
primarily via diffusion from the silt into
the overlying gravel and by advection in
soils at the top of the screen.
The PneuLog test is repeatable, and
multiple deployments can track cleanup
progress closely. When performed in a
number of wells, this approach provides a
more complete and accurate site
characterization and conceptual model
for design or optimization of SVE
systems. In addition, detailed fate and
transport models can be coupled with
measurements of soil permeability and
contaminant source characteristics to
provide estimates for cleanup time. For
more information, contact Jim Cummings
(EPA/Technology Innovation Office) at
703-603-7197 or e-mail
cummings.james@epa.gov, or Dr. Lloyd
Stewart (Praxis Environmental Tech., Inc.)
at 877-763-8564 or e-mail
PneuLog@Praxis-Enviro .com.
Joint technical
Remediation Seminars
to be Held in June
EPA's Technology Innovation Office
(TIO) and the Ground Water Remediation
Technologies Analysis Center (GWRTAC)
will present back-to-back, one-day
seminars on June 6-7, 2000 at the
Radisson Boston Hotel in Boston, MA.
• GWRTAC's 4th "Advances in
Innovative Ground-Water
Remediation Technologies"
conference on June 6th will
include presentations from
practitioners involved in various
in situ ground-water remediation
technologies, including
permeable reactive barriers, in situ
flushing, thermal enhancement, in
situ chemical oxidation, ground-
water recirculation wells, metals
remediation, and bioremediation.
• TIO's "/« Situ Thermal
Conference" on June 7th will
focus on fundamental principles,
design considerations, limitations,
and case studies of in situ thermal
processes for remediation of
dense, non-aqueous phase liquids.
Technology topics will include
dynamic underground stripping,
electrical conductive heating,
radio frequency heating, and
six-phase electrical heating.
For further information, visit TIO's
Web site at www.clu-in.org or
GWRTAC's Web site at
www.gwrtac.org. To register for either
or both of these seminars, contact
Karen Devlin (Philip Services) at
215-643-5466 or e-mail
kdevlin@philipinc.com.
Mention of trade or commercial products does not constitute endorsement by the U.S. Environmental Protection Agency.
cvEPA
United States
Environmental Protection Agency
National Service Center for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242
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EPA 542-N-00-003
May 2000
Issue No. 37
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