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INNOVATIVE RESEARCH FOR A SUSTAINABLE FUTURE
Innovative Capping Technology to Prevent the Migration of Toxic
Chemicals from Contaminated Sediments
Research Value:
Contaminated sediments is a
problem in many U.S. waterways.
Nearly 40% of the rivers and
streams in the U.S. are too
polluted for fishing and
swimming. Contaminants in
sediments involve both
microorganisms and toxic
chemicals. Many widespread
persistent toxic chemicals are
present in sediments, including
polychlorinated biphenyls
(PCBs), poly cyclic aromatic
hydrocarbons (PAHs), and heavy
metals. These chemicals can be
released into the water above, and
can bioaccumulate in the food
web to levels in fish that pose a
risk to the wildlife and humans
that eat them. Fish advisories,
warnings not to eat fish caught in
our lakes and streams, have
become increasingly common.
Capping is a common strategy
for decreasing the risk associated
with contaminated sediments in
lakes and streams. Historically,
caps have been designed to
physically isolate contaminated
sediments and prevent the
transport of contaminants from
sediments into the water above
them, to aquatic organisms, and to
wildlife and humans, with sand
caps being common. Questions
remain concerning the
effectiveness of traditional sand
capping. These questions include
the vertical transport of
contaminants through the sand
cap to the overlying surface water.
New innovative capping
materials have been developed
that may address some of the
questions with traditional sand
caps. One of these new
®
materials, Aquablok is a clay-
based polymer composite,
designed to swell and form a
continuous and highly
impermeable barrier. Other
technologies involve the use of
"active" material such as
activated carbon or organoclays
to retard or sequester the
contaminants as they migrate
vertically through the cap.
Applying capping materials with a
clamshell bucket
Research Details:
EPA land risk management
researchers are leading efforts to
determine if these innovations can
fulfill their promise to better
protect human and wildlife health.
Goals in evaluating these
innovative capping materials
include:
• Evaluate how the performance
of each capping technology is
affected by gas generation
below the cap.
• Develop improved methods for
collecting and measuring
sediment gas generation.
• Evaluate the degree to which
aquatic organisms affect cap
performance.
• Investigate how the presence of
a cap affects the number and
diversity of organisms in a
contaminated area.
• Evaluate the physical stability
of each type of cap, and the
fate and transport of
contaminants overtime.
Joint Research with Academia:
Anacostia River Capping Study
A field study at the Anacostia
River in Washington, B.C. was
conducted with EPA's Southwest
Hazardous Substance Research
Center to evaluate the
(S)
performance of an AquaBlok
cap compared to a sand cap and
unaltered sediment. The study
included an evaluation of the
physical stability of the cap, the
effect of the cap on the
groundwater and sediment
interface, the impacts of the cap
on aquatic organisms, and the
impact of these organisms on
cap performance. Results of the
study are available in the report,
U.S. Environmental Protection Agency
Office of Research and Development (ORD), National Risk Management Research Laboratory (NRMRL)
Land Remediation and Pollution Control Division (LRPCD)
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Demonstration of the AquaBlok
Sediment Capping Technology.
Studying sediment properties
Joint Research with EPA
Region and State: Chattanooga
Creek Cap Monitoring Study
EPA land risk management
researchers are working with
EPA Region IV and with the
Department of Environmental
Conservation in Tennessee to
monitor an installed AquaBlok
cap in a section of Chattanooga
Creek that has seen decades of
industrial pollution from coal tar
and creosote.
Joint Research with EPA's
GLNPO and ACOE: Sorbent
Column Studies
EPA is working in cooperation
with the Great Lakes National
Program Office (GLNPO) and
the U.S. Army Corps of
Engineers (ACOE) to evaluate
various sorbents for possible use
on contaminated sites in the
Great Lakes area. The ultimate
goal of this research is to refine
the design process for more
effective caps.
Joint Research with
Department of Defense (DOD):
Cap Evaluation Studies
EPA is working in integrated
collaborative efforts with the
U.S. DOD (which has programs
for environmental research and
environmental security), the
ACOE, and EPA's Regional
Offices to improve cap designs
and their cost effectiveness.
In other DOD-related efforts,
EPA has evaluated an innovative
bauxite cap for containing
mercury contaminated sediments,
and is currently evaluating the
impact of propeller wash on the
stability of sediment caps.
Placing a reactive cap
Outcomes and Impacts:
Innovative capping technology
research is helping to provide
more options to reduce the risk to
humans and benthic organisms
from contaminated sediments.
This research is providing new
information and tools that are
being used by EPA's Office of
Superfund Remediation and
Technology Innovation and
EPA's regional staff to select the
most environmentally and cost
effective remediation techniques
at contaminated sediment sites.
Future research on capping and
other sediment remediation
projects will examine
incorporation of tools such as
Life Cycle Assessment (LCA)
into efforts for sustainable
sediment management.
LAND RESEARCH PROGRAM
WEB SITE: www.epa.qov/nrmrl/lrpcd
CONTACTS
Dennis Timberlake, Technical
Inquiries. 513-569-7547, EPA/
ORD/ LRPCD/SSMB
timberlake.dennis(@,epa.gov.
EdBarth, Technical Inquiries.
513-569-7669, EPA/ORD/
LRPCD/SSMB barth.ed(@,epa.gov
Roger Yeardley, Communications.
513-569-7548. EPA/ ORD/ LRPCD
veardlev.roger(@,epa.gov
REFERENCES
Evaluation of Sediment Agitation and
Mixing into the Surrounding Water
Column from Capping Activities at the
Wyckoff/Eagle Harbor Superfund Site,
EPA/540/R-05/013, July 2006.
http://www.epa. gov/ORD/NRMRL/pubs
/540r05013/540r05013.pdf
Demonstration of the AquaBlok
Sediment Capping Technology
(Innovative Technology Evaluation
Report) EPA/540/R-07/008, Sept. 2007.
http://www.epa. gov/ORD/NRMRL/pubs
/540r07008/540R07008.pdf
National Risk Management Research Laboratory
Land Remediation and Pollution Control Division
EPA/600/F-11/009
June 2011
www.epa.gov/nrmrl
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