United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-99-003
May 1999
Issue No. 33
CONTENTS
"Snow Cap" Used for
Sediment Remediation page 1
DOE Comparison of
Landfill Cover Designs page 2
InSituOzonationto
Degrade Recalcitrant
Compounds page 3
Brownfields Workshops page 4
The Applied Technologies
Newsletter for Superfund
Removals & Remedial
Actions & RCRA Corrective
Action
ABOUT THIS ISSUE
This issue highlights
innovative techniques for
containment and treatment of
soil, sediment, and ground
water contaminants under
challenging site conditions.
"Snow Cap" Used for
Sediment Remediation
by Lisa Gutknecht, Wisconsin
Department of Natural Resources,
and Mick Warner, RMT, Inc.
A new method was employed for
constructing a cap over lead-
contaminated sediments in a shallow,
oxbow lake in Wisconsin. Using a
geomembrane and sand, a "snow cap"
was constructed during the winter, which
then slowly settled over the lake in the
spring as the snow melted. In addition to
costing significantly less than
conventional (and environmentally
invasive) sediment dredging in terms of
both funding and time resources, this
technique offers the advantage of
providing a safe habitat for existing fish
populations.
The snow cap was installed during
February 1997 at a former battery
reclaiming site near Wausau, WI. The
capped area consists of a four-acre oxbow
lake adjacent to the Rib River, which
serves as an important breeding habitat
for small fish. The lake is not part of the
river channel, but includes flow-
through areas. During spring
thaw and heavy rain events, the
lake is inundated by the
adjacent river. Soft sediment
impacted with lead has covered
the lake bottom at an average
thickness of two feet. This
sediment consists of fine
particles that could be re-
suspended easily if disturbed.
Prior to treatment, lead
concentrations in the sediment
ranged as high as 540 mg/kg at
a depth of 0-0.5 feet, and 850
mg/kg at 0.5-1.3 feet.
The four-layer composite cap
used for this site includes a
geotextile and sand blanket over the
impacted area, and a second layer of
geotextile and rock "islands." The
geotextile keeps sediment from
migrating into the sand, and sand from
migrating into the rock "islands" that
serve as a spawning habitat.
Snowmobiles were used to pack the snow
and increase the ice thickness from 6 to
24 inches, thus providing support for
heavy, wheeled construction equipment.
By constructing the cap on top of the
frozen lake, the creation of a "mud wall"
(typically formed when water capping
begins at a shoreline and pushes the cap
materials outward over the sediment) was
avoided. The formation of such mud
walls commonly re-suspends
contaminated sediment and prevents
adequate contaminant containment.
Installation of the cap on top of the
frozen lake also allows the geotextile to
be spread during a longer time frame,
overlapped uniformly, inspected prior to
covering, and placed without sediment
disturbance (Figure 1).
Islands for providing habitat for small
fish and other benthic organisms were
installed at nine locations within the
[continued on page 2]
Figure 1. Spreading Geotextile over Frozen Lake
Recycled/Recyclable
Printed with Soy/Canola Ink on paper that
contains at least 50% recycled fiber
-------
[continued from page 1]
lake. These benthic islands consist of
irregularly shaped rock on top of the sand.
A second layer of geotextile material was
placed between the rock and sand to
prevent settling of the rock. The islands
were constructed of a total of 300 tons of
rock covering approximately 10 percent
of the lake bottom. Rock layers were
placed at the inlet of a small tributary to
the river's oxbow and at the small outlet
of the oxbow to prevent erosion of the
sand cap from flows in these areas.
Analysis of field data collected at five
sampling locations during March 1999
found current lead concentrations in the
water column to be at background (3-6
mg/kg) or non-detect levels, indicating
that no impacted sediment or sediment
interstitial water is migrating through the
geotextile or upper sand layer of the cap.
In addition, populations of benthic
organisms were noted in the shallow water
areas in leaf litter, and submergent
vegetation is becoming established on the
new substrate. To ensure the cap is
performing effectively, Wausau Steel will
perform annual inspections of the cap's
physical integrity, and the Wisconsin
Department of Natural Resources will
conduct periodic testing of the pore water.
In comparison to alternative dredging and
removal of the contaminated sediment, it
is estimated that this remediation
approach cost approximately one-third of
the cost to remove the sediment, for a
savings of $ 1 million.
New technologies such as the snow cap
are needed in the Great Lake ecosystem to
address the variety of toxicants found in
the area. This project constituted the first
full-scale, full-coverage sediment cap
installed in Wisconsin. The feasibility of
installing snow caps at other sites in the
future will be evaluated on a site-by-site
basis, taking into account the
hydrological characteristics of the site.
Contact Lisa Gutknecht (Wisconsin
Department of Natural Resources) at 715-
359-6514 or E-mail
gutknl@dnr.state.wi.us, or Mick Warner
(RMT, Inc.) at 608-831-4444 or E-mail
mick.warner@rmtinc.com, for more
information.
Annual Status Report on Cleanups
The U.S. Environmental Protection Agency has issued a new report entitled Treatment
Technologies for Site Cleanup: Annual Status Report (Ninth Edition). The report documents
the status, as of mid 1998, of treatment technology applications at over 900 soil and ground
water cleanup projects in the Superfund program or at selected RCRA corrective action, U.S.
Department of Energy, or U.S. Department of Defense sites. In addition to updates from the
previous edition, the report includes information on 79 records of decision completed in 1996-
1997, and 217 incineration and solidification/stabilization proj ects. For frequently selected
technologies, the report analyzes selection trends over time, contaminant groups addressed,
quantities of soil treated, and project implementation status. Specific site information for each
technology application has been incorporated into the EPA REACH IT on-line database,
available on the Internet at http: //www. epareachit. org. The entire report will be available on
the Hazardous Waste Clean-Up Information Home Page at http://clu-in.org. Copies may also
be ordered by phone from EPA's National Service Center for Environmental Publications at 1 -
800-490-9198 by referring to the document number: EPA-542-R-99-001.
DOE Comparison of
Landfill Cover Designs
by Stephen Dwyer, Sandia National
Laboratories
The U.S. Department of Energy (DOE)
Sandia National Laboratories is
conducting a five-year, large-scale field
demonstration comparing landfill cover
designs at a test facility on Kirtland Air
Force Base in Albuquerque, MM. This
demonstration, known as the Alternative
Landfill Cover Demonstration (ALCD), is
evaluating two conventional and four
alternative cover designs based on their
respective water balance performance,
ease of construction, and cost. Analysis of
the first two years of data collected in this
five-year demonstration are confirming
earlier field experiences that conventional
cover designs under RCRA Subtitle C and
D are vulnerable to regional geologic and
climatic conditions. To date, higher
performance is exhibited by two of the
less costly alternative designs.
The ALCD test covers were installed side-
by-side for direct comparison. Two
baseline conventional covers were
constructed, one in accordance with
performance standards for RCRA Subtitle
D soil covers and the second for Subtitle
C compacted clay covers. Alternative
designs include a geosynthetic clay liner,
capillary barrier, anisotropic barrier, and
evapotranspiration cover. Each test cover
is 13 meters wide by 100 meters long,
with a 50-meter, 5 percent slope in all
layers. One side of the slope is monitored
under ambient conditions, while a
sprinkler system provides additional
moisture on the other side to facilitate
stress testing.
The conventional soil cover is 60 cm
thick, including a 45-cm bottom layer of
compacted soil and a 15 cm top layer of
loose topsoil. The conventional
compacted clay cover is 1.5 m thick,
consisting of a 60-cm native soil lower
barrier (composed of 6 percent bentonite
by weight), 40-mil linear low-density
polyethylene geomembrane, 30-cm thick
middle drainage layer of sand, a
geotextile to filter between the drainage
and top layer, and a 60-cm vegetation
layer (45 cm of native soil and 15 cm of
topsoil) on top.
The alternative geosynthetic clay cover is
identical to the compacted clay cover
with the exception that the clay barrier
layer is replaced with a commercially-
purchased geosynthetic clay liner
(composed of two nonwoven fabrics
sandwiching a layer of bentonite). The
capillary barrier system, which is intended
to minimize hydraulic conductivity
through the cover, consists of a 30 cm-
thick upper layer of topsoil; 22 cm-thick
upper lateral drainage layer of gravel
[continued on page 3]
-------
[continued from page 2]
overlain by 8 cm of sand; 45 cm-thick
barrier soil layer; and a 30 cm-thick lower
drainage layer of sand.
The anisotropic barrier attempts to limit
downward movement of water while
encouraging lateral movement of water
through the layering of capillary barriers.
This system consists of a 15-cm top
vegetation layer of local topsoil and pea
gravel; 60-cm layer of native soil; 15-cm
interface layer of fine sand; and 15-cm
sublayer of pea gravel. The fourth
alternative design — the
evapotranspiration cover — is a soil cover
with an engineered vegetative covering
that works to encourage water storage
while enhancing evapotranspiration. This
90-cm cover consists of a 75-cm
compacted bottom layer with a 15-cm top
layer of loosely packed topsoil.
Continuous water balance and
meteorological data have been collected
over the past two years. In addition,
periodic measurements of vegetation
cover, biomass, leaf area index, and
species composition are collected. Data
analysis indicates that the RCRA Subtitle
D soil cover is experiencing problems,
with a decreasing ability to minimize
percolation resulting from desiccation
cracking and freeze/thaw cycles.
Similarly, but not as rapidly, the
compacted clay cover is exhibiting
increased percolation because the
geomembrane is hampering the ability of
the barrier layer to dry by evaporation. Of
the alternative covers, the geosynthetic
clay liner cover is not performing as well
as expected; eight 1-cm2 defects in the
geomembrane (possibly caused by
construction damage, bentonite leaching,
or root intrusion) have been identified.
For the capillary barrier, the percolation
rate for the first year was higher than
expected, but has slowed significantly.
These changing percolation rates are
believed to result from vertical movement
of unsaturated flow that is increasingly
retarded as the upper vegetation layer
thickens and increases the
evapotranspiration rate.
The anisotropic barrier and
evapotranspiration cover are performing
well, with decreased percolation rates
resulting from increasing vegetation
growth and associated transpiration rates.
Percolation rates progressively have
decreased to rates below that of the
compacted clay cover. These covers cost
over 50 percent less than the compacted
clay cover, with a higher long-term
performance expected. For more
information, contact Stephen Dwyer
(Sandia National Laboratories) at 505-
844-0595 or E-mail sfdwyer@sandia.gov.
In Situ Ozonation to
Degrade Recalcitrant
Compounds
by Megan Cambridge, CAL EPA,
and Ron Jensen, Southern
California Edison
Possibly the largest in situ application of
ozone technology in the country to
remediate soil and ground water began
operating earlier this year at a former
manufactured gas facility in Long Beach,
CA, after a successful pilot-scale
application. Clean-up activities are
challenged by a complex utility and
transportation infrastructure adjacent to
major surface waters. Initial dissolved
contaminant concentrations ranging as
high as 912,000 (ig/1 for total petroleum
hydrocarbons (TPH), 4,820 (ig/1 for
benzene, 20,000 (ig/1 for napthalene, and
340 (ig/1 for benzo(a)pyrene were reduced
by greater than 50 percent on average
over the first three months of operation.
The former Long Beach II Manufactured
Gas Plant site, which was used by
Southern California Edison (SCE) from
1902 to 1913 to produce synthetic gas
from oil and coal, currently is used as an
elevated roadway interchange and for oil
and gas production. Residues generated
from the original gas manufacturing
operations consist of tar, oils, and
lampblack containing polycyclic
aromatic hydrocarbons (PAHs). Early site
investigations revealed petroleum and
PAHs in soil and ground water.
Concentrations of the primary
constituents were as high as 2,484 mg/kg
for total PAHs, 100 mg/kg for
benzo(a)pyrene, and 27,800 mg/kg for
TPH in soil. Risk assessment, however,
determined that only soils required
remediation.
Wedged between the Long Beach Freeway
and the Los Angeles River, the site
comprises a 340- by 230-foot strip of land
with an extensive system of buried high-
power transmission cables and elevated
bridges. Detailed site surveys to locate all
of the subsurface utilities were critical
prior to construction of the system, which
began in October 1998. A total of 31
vertical sparging wells, constructed of
Teflon, Viton, and 316 stainless steel and
screened at a depth of 25 feet, were
installed throughout the plume. In
addition, a single 360-foot horizontal well
with a 135-foot screened section in the
middle was installed through the center of
the plume at about 6 feet below the water
table.
Two ozone generators with a combined
capability of delivering 52 pounds of
ozone per day are used to deliver a
mixture of 5-10 percent ozone and 90-95
percent oxygen. The compressed gas
stream is injected into the soil through the
wells at a rate of 7.5 cubic feet per minute
and injection pressure of 20 pounds per
square inch gauge. A soil vapor
extraction system (SVE) is in place above
the injection wells to control emissions of
low molecular weight hydrocarbons and
ozone gas from the treatment area. All
above-ground ozone generation,
compression, and vacuum blower
equipment functions, as well as ozone
emission monitors, are integrated in a
computerized system that monitors and
directs the activation, modulation, and
shut-down of the treatment system (Figure
2).
Operation of this system involves
intermittent ozone injection to promote
both chemical and biological oxidation.
In any areas of hot spots, the ozone
concentration in the injection stream can
be increased to as high as 8-12 percent,
continuously delivered. SCE is
implementing a four-pronged monitoring
program comprising continuous process
parameter measurements, weekly
measurement of carbon dioxide levels
(directly reflecting hydrocarbon
degradation), monthly ground water
sampling, and quarterly soil sampling.
The California Environmental Protection
Agency, Department of Toxic Substances
Control (CAL EPA/DTSC) selected this
[continued on page 4]
-------
Tech Trends is on the NET!
View or download it from:
http://www.epa.gov/tio/pubitech.html
http://clu-in.org
Tech Trends welcomes comments, contributions,
and new subscriptions. Address correspondence
to:
Tech Trends,
8601 Georgia Avenue, Suite 500
Silver Spring, Maryland 20910
Fax: 301-589-8487
[continued from page 3]
site as a pilot project in the state's
Expedited Remedial Action Program,
which was established by California's
legislature to test regulatory policies for
the remediation of contaminated
properties. SCE has worked closely with
CAL EPA/DTSC since 1994 to
characterize and remediate this site, which
now is owned by the Los Angeles County
Flood Control District and City of Long
Beach. The system was constructed by IT
Corporation, which has conducted
extensive research and development of
ozonation technology. Construction and
operation of this system, which is
expected to continue until 2000, has been
estimated to cost about $1 million. For
additional
information,
contact Megan
Cambridge (CAL
EPA/DTSC) at
916-255-3727 or
E-mail
mcambrid@
dtsc.ca.gov, Ron
Jensen (SCE) at
626-302-9561 or
E-mail
jensenrd@sce.com,
or Jay Dablow (IT
Corp.) at 949-660-
7598 or E-mail
jdablow@
theitgroup.com.
Figure 2. In Situ Ozonation System
SVE
Brownfields
Workshops
Workshops providing an overview of
environmental assessment and cleanup
strategies based on cost, risk, and
intended land use goals will be presented
at several locations this year. The
workshops will address the use of costs,
regulations, and risks to steer site
assessment techniques and selection of
cleanup strategies; designing sampling
strategies; and understanding
relationships between cleanup operations,
risk, and redevelopment economics.
Workshop information will be useful to
local government officials, property
owners, interested citizens, developers,
financiers, regulators, and environmental
contractors. Locations and dates for
the workshops, which are offered by
the Great Plains/Rocky Mountain
Hazardous Substance Research Center
in partnership with EPA technical
assistance and outreach programs, are:
• Sioux Falls, SD - May 4, 1999
• Des Moines, IA - May 6, 1999
• St. Louis, MO - May 24, 1999
• Salt Lake City, UT - June 3,1999,
Denver, CO - July 8,1999.
For more information, visit the Web at
http://www.engg.ksu.edu/HSRC/
Workshops.html or contact Terrie
Boguski (Kansas State University) at
913-780-3328.
United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-99-003
May 1999
Issue No. 33
-EPA TECH TRENDS
------- |