United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-99-001
February 1999
Issue No. 32
CONTENTS
Innovative Freeze Barrier
Installation at ORNL page 1
Evaluation of Alternative
Earthen Landfill Covers page 2
Mini-Cap for Landfill
Cover Monitoring page 3
PRB Training Course page 4
The Applied Technologies
Newsletter for Superfund
Removals & Remedial
Actions & RCRA Corrective
Action
ABOUT THIS ISSUE
This issue highlights
innovative methods for in situ
containment of hazardous
wastes and containment
monitoring.
TRENDS
Innovative Freeze
Barrier Installation at
ORNL
by Elizabeth Phillips, U.S.
Department of Energy, and
Michael Harper, BechtelJacobs
Co. LLC
Demonstration of an innovative frozen
soil barrier technology for containment
of subsurface radioactive contaminants
was conducted at Oak Ridge National
Laboratory (ORNL) in Oak Ridge, TN,
from September 1996 through September
1998. Ground water monitoring and dye
tracer results indicate that the frozen soil
barrier hydraulically isolates a hazardous
waste area from the surrounding area.
Frozen soil barrier technology for
containment of subsurface contaminants
consists of installing subsurface heat
transfer devices around a contaminant
source to freeze soil pore water, which
creates a frozen soil boundary that is
impervious to ground water movement.
The frozen soil barrier isolates the
contaminant source from the surrounding
ground water, preventing transport of
contaminants to adjacent areas. The
barrier is maintained in situ until the
source of contamination is physically
removed, treated, decayed to acceptable
levels, or otherwise remediated. At that
point, the system is powered down and
the frozen barrier eventually thaws. If
the barrier is removed prior to
remediation, the site will return to its pre-
barrier configuration, as will the
mechanism of contaminant transport
from the source.
The technology demonstrated at ORNL
involves the installation of
thermoprobes, which are subsurface heat
removal devices. A conventional
thermoprobe used in cold climates
removes heat from soil by virtue of
being a thermosyphon, using a two-
phase working fluid to remove heat
passively without the need for an
external power supply. In contrast, an
innovative "hybrid thermoprobe"
technology was developed by Arctic
Foundations, Inc., for use in the warmer
climate at ORNL. The technology
operates in a closed, two-phase system
that operates in a passive-active mode
requiring external power for part of the
heat removal cycle.
The hybrid system consists of multiple
thermoprobes, each containing a two-
phase passive refrigerant (carbon
dioxide), a conventional refrigeration
unit (using R-404A refrigerant), an
interconnecting piping system, and a
temperature monitoring and control
system (Figure 1). Once installed around
a source of contamination, the array of
thermoprobes is connected to the
refrigeration system by a distributive
manifold. Liquid-to-gas phase change
of the passive refrigerant within each
thermoprobe removes heat from the
surrounding soil. The conventional
refrigeration portion of the system then
functions to remove heat from each
thermoprobe, via internal heat
exchangers, for dissipation to the
atmosphere. When the soil matrix
adjacent to the thermoprobes reaches
0°C, soil particles are bonded together as
soil moisture freezes. Additional
[continued on page 2]
o
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Figure 1. Typical Thermoprobe for Frozen Barrier
Construction
[continued from page 1]
cooling is applied until the frozen region
around each thermoprobe begins to
expand and build outward, coalescing
with frozen regions developing around
the other thermoprobes until an
impermeable frozen soil barrier is formed.
The ORNL demonstration site consisted
of an unlined, backfilled, and capped
earthen impoundment used from 1958
through 1961 for retention of liquid
radioactive wastes generated from
operation of an experimental nuclear
reactor. 1984 data analysis
estimated that the
impoundment contained
approximately 75 Curies
(Ci) of '"Strontium and 15
Ci of 137Cesium in the
buried sediments.
In the ORNL hybrid
thermoprobe system, a total
of 50 thermoprobes were
placed on six-foot centers
around the impoundment.
Each thermoprobe freezes a
column with a six-foot
radius, thus creating a
barrier twelve feet thick.
The frozen barrier wall
around the impoundment
was established during a
"freeze-down" period of
approximately 18 weeks.
The frozen zone ranges
from grade to a depth of 30
feet (the entire subsurface
length of the thermoprobe)
or more below grade around
the original 75 by 80-foot
perimeter of the
impoundment. With the
exception of a one-time
anomaly attributed to a
temporary reverse gradient
of ground water in a former
sump pump line, ground
water movement through
the barrier has not been detected.
The project cost approximately
$1,809,000, including design,
installation, startup, system operation,
engineering oversight, site infrastructure
upgrades, and pre- and post-barrier
verification studies. The system requires
approximately 288 kilowatt-hours of
electrical power per day for maintaining
the frozen soil barrier, costing
approximately $15 per day at ORNL
rates.
Although the demonstration is complete,
the barrier will be maintained for several
years until a final remediation decision is
made and implemented. Complete results
of the demonstration will be published
through EPA's Superfund Innovative
Technology Evaluation (SITE) Program.
For additional information, contact
Elizabeth Phillips (U.S. Department of
Energy) at 423-241-6172 or E-mail
phillipsec@oro.doe.gov, or Michael
Harper (Bechtel Jacobs Co. LLC) at 423-
574-7299 or E-mail
harperma@bechteljacobs.org.
Evaluation of
Alternative Earthen
Landfill Covers
by Steven Rock, U.S. EPA National Risk
Management Research Laboratory, and
Bill Albright, Desert Research Institute
A new program is underway to develop
basic design guidance and numerical
tools for site owners, design engineers,
and regulators in evaluating the
performance of alternative earthen
landfill covers. The Alternative Cover
Assessment Program (ACAP)—a
cooperative partnership of industry,
government, and research institutions
organized under the Remediation
Technologies Development Forum's
Phytoremediation Action Team—will be
implemented in four phases at 10 active
disposal sites across the country in an
effort to evaluate evapotranspiration and
capillary break systems.
Phase I ACAP activities, which began in
March 1998, consist of an initial review
of current data collection efforts and
numerical modeling capabilities. In
Phase II, the design, construction, and
operation of a network of 10 cover testing
facilities will occur. Phase III will
combine Phase II field results with
improved numerical models to predict the
[continued on page 3]
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[continued from page 2]
long-term (over 500 years) performance
of alternative cover systems at the
selected cover testing sites. Performance
predictions will be made for a wide range
of expected climatic, geologic,
geographic, and hydrologic variables.
The final phase, which is expected to
begin in early 2003, will involve
development of comprehensive guidance
documentation on alternative cover
At each location, one or more full-scale
(in depth) cover designs will be
constructed in 200 m2 water-balance
lysimeters. Vadose zone monitoring and
biological and climatological
observations will provide data
concerning the movement of soil
moisture, local climate conditions, and
plant community activities. Figure 2
illustrates the anticipated design of each
monitoring station.
Figure 2. Vadose Zone Monitoring Station
systems. Resulting data will be
accessible to federal and state agencies
for evaluating alternative covers for
specific applications.
The process of selecting sites at which to
construct the ACAP testing facilities is
underway. Facilities will be located at, or
near, disposal sites with differing geology
and climates. Site characterization at
each location will involve collection of
local data on:
Climate variables such as
precipitation quantity, type, and
seasonality, as well as intensity,
temperature, and humidity;
Plant community variables,
including species, density, a leaf area
index, phenology, and rooting
depths; and
Topographic features such as slope,
exposure, surface drainage, and depth
to ground water.
Field efforts will focus
on directly measuring
the performance of the
tested covers and
movement of ground
water through the
various cover designs.
All sites will be
monitored through
uniform methods
using similar
technologies.
Climatic parameters
used for performance
testing will include
wind speed and
direction, air temperature, precipitation,
solar radiation, humidity, and snowfall/
snowpack. Plant-related parameters will
include minirhizotron sampling
(photographic imaging through
transparent tubes inserted into the soil) of
root distribution, a leaf area index, and
plant biomass. Soil parameters will
include:
Lysimeter drainage (tipping bucket
recorder, stage recorder, and dosing
siphon);
Continuous integrated water content
measurements (electrical resistance,
capacitance, and reflectance);
Electronic soil water pressure
(tensiometer, heat dissipation, and
gypsum block);
Gas sampling, where appropriate;
Soil temperature profiles, where
appropriate; and
Drainage water quality.
The ACAP is expected to result in cost-
effective alternative cover designs for the
study sites, while providing guidelines
and criteria for the development of
designs at other disposal sites.
Additionally, the project will help to
improve numerical predictions for
landfill cover performance and the
technologies available for landfill cover
performance monitoring. ACAP members
will meet in San Francisco, CA, March
22-23, 1999, to discuss the program.
Contact Kelly Madalinski (U.S. EPA,
Technology Innovation Office) at 703-
603-990 lor E-mail
madalinski.kelly@epa.gov for more
information.
Mini-Cap for Landfill
Cover Monitoring
by Thomas Bloom, U.S. EPA,
Region 5
The U.S. EPA, U.S. Army Corps of
Engineers, and Ohio Environmental
Protection Agency have implemented a
simple and innovative way to test the
permeability of a geosynthetic clay cap
and associated cap components years
after construction completion. This
method, which has been employed since
September 1998 at the Fultz Landfill in
Byesville, OH, involves the construction
of a miniature geosynthetic clay
composite cap identical with and
adjacent to the full-scale landfill cover.
In addition to permeability testing, the
mini-cap provides for evaluation of the
long-term effects of freezing and thawing
conditions as they relate to the hydraulic
conductivity of the cover system. This
approach is an inexpensive (less than
$10,000) alternative to digging up
sections of expensive cover systems when
performance evaluation is needed.
Although a mini-cap can be implemented
at any time during remedial activities,
[continued on page 4]
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[continued from page 3]
plans for implementing a mini-cap at the
Fultz Landfill were incorporated during
the early design phase of remediation. In
order to gain a complete understanding of
site condition changes over time, the
mini-cap was constructed simultaneous to
the construction of the cover system. A
single lysimeter consisting of a separate
and complete 25 by 20-foot cap section
was installed above the frostline, outside
the area to be covered. A 4-foot stand
pipe is included in the lysimeter for use
in monitoring permeability, and a pan
was installed to collect water that has
leaked through the cover components
over a certain period of time. A small
piece of the mini-cap can be extracted by
drilling and examined to identify any cap
damage or impacts from freeze/thaw
cycles. December 1, 1998, testing of the
mini-cap indicated that no leakage has
taken place.
In addition to providing a tool for as-
needed testing of the landfill cover
performance, regulators anticipate that
the lysimeter will contribute significantly
to evaluating the effectiveness of the full-
scale landfill cover during the site's
post-closure care, such as five-year
review. Contact Thomas Bloom (U.S.
EPA, Region 5) at 312-886-1967 orE-
mail bloom.thomas@epa.gov, or Raj
Rajaram (Tetra Tech) at 847-818-7189 or
E-mail rajarar@ttemi.com for more
information.
PRB training Course
In Situ Permeable Reactive Barriers:
Application and Deployment is a new
course that will be offered in or near the
10 cities where EPA's regional offices are
located. The course is designed to assist
regulatory professionals in overseeing
the design, implementation, and
monitoring of ground-water remedies
involving permeable reactive barriers
(PRBs), and to consolidate the
numerous efforts that have provided
design and regulatory guidance on
PRB deployment. Although geared
toward state and federal regulators,
industry representatives and
consultants are encouraged to attend.
The Remediation Technologies
Development Forum (RTDF) PRB
Action Team, Interstate Technology
Regulatory Cooperation (ITRC)
Permeable Barriers Working Group,
U.S. EPA Technology Innovation
Office, and U.S. EPA National Risk
Management Research Laboratory
partnered in development of the
course. During 1999, the course will
be offered in Boston, MA, on June 22-
23; Seattle, WA, on August 10-11;
Philadelphia, PA, on September 21-22;
and Dallas, TX, on November 16-17.
Details about the course and
registration will be posted on the PRB
Action Team home page of the RTDF
Web site (www.rtdf.org/barriers.htm) as
they become available.
United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-99-001
February 1999
Issue No. 32
-EPA TECH TRENDS
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