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A Citizens' Guide '
Cleaning Up
Contaminated
Sediment
Drafted by the Lake Michigan Federation
Written by jerry Sullivan
Edited by Kathy Bero and Steve Skavroneck
Prepared for the U.S. Environmental Protection Agency
Great Lakes National Program Office under grant
GL995236.
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
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INTRODUCTION 4
HOW THE ARCS PROGRAM WORKED ; 6
WHAT HARM CAN IT DO?: THE QUESTION OF RISK ASSESSMENT 10
WHAT CAN BE DONE?:THE TECHNOLOGY OF REMEDIATION 13
REMOVING SEDIMENT IS
TREATMENT TECHNOLOGIES 17
PUBLIC INVOLVEMENT 19
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Sediments have been collecting on the bottoms
of the Great Lakes and in the beds of
tributary rivers ever since the lakes were
formed by the melting of the glaciers thou-
sands of years ago, The loose, unconsolidated
particles that make up the sediment may origi-
nate in soil worn away by physical or chemical
erosion, or they may come from the decompo-
sition of shells or wood chips.
Wind, water, ice- and gravity carry these
particles from their place of origin. Once they
reach a river or lake, currents and storm waves
can keep them suspended, often carrying them
great distances. But in quiet waters, they sink
to the bottom.
Before large numbers of people came to
the Great Lakes Basin, the natural processes of
sedimentation created changes in the lakes and
their tributaries, but they did no harm. The
industrialization of the basin changed that. In
the first century or so of industrial and urban
development, we paid little attention to the
wastes our prosperity created, The usual
approach was to run a pipe to the nearest
river bank or lakeshore and pump the waste
directly into the water
Over the decades, heavy metals and toxic
organic chemicals both municipal and indus-
trial wastes and herbicides and pesticides from
farm runoff mixed-with the particles of
rock, soil, and decomposing wood and shell in
the sediments collecting in rivers and harbors
in the Great Lakes Basin.
Even after serious clean-up efforts began on
the lakes in the late 1960s,/fittle attention was
paid to the toxins hiding in the muds on the
bottom. The obvious first priority was stopping
the discharge of new contaminants from facto-
ry outfalls and municipal wastewater facilities.
Many people thought that lake bottoms were a
safe place for toxic materials.
The environmental problems caused by con-
taminated sediments first began to be noticed
in the early 1980s. One clue was the increase
in concentrations of the pesticide DDT and the
widely used group of industrial chemicals called
RGBs in the tfssues of Great Lakes fish, The
use of DDT had been forbidden in the United
States since 1972 and RGBs had been banned
except for use in closed systems in 1979,
In the years immediately following the ban, lev-
els of these chemicals in the tissues offish and
other animals dropped. But then, with levels still
unacceptably high, the decline stopped, In some
cases, levels actually began to go up again,
Studying this alarming trend, scientists dis-
covered that some of the increase came from
the air Chemicals, some from sources hun-
dreds, even thousands of miles away, were
being deposited in the lakes. Other scientists
turned their attention to the bottoms of our
lakes^and rivers where toxins, deposited during
decades of environmental carelessness, were
hiding in the mud.
River beds and lake bottoms are not quiet
places. Storms and propellers of passing ships
often stir up the sediments, resuspendmg con-
taminants already buried. Bottom-dwelling
animals add more disturbance. Many of these
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animals feed in the mud, taking in toxins and
storing them in their bodies. When sludge
worms or insect larvae from this bottom-
dwelling or "benthic" community are
eaten by larger animals, the toxics are part of
the meal. At each link in the food chain the
concentrations of toxins get higher; in some
instances, thousands of times higher.
At the top of the Great Lakes food chain,
we find large lake trout and salmon that are
considered unsafe to eat because of the heavy
concentrations of toxic substances in their tis-
sues. Fish-eating birds nesting around the Great
Lakes, among them bald eagles, double-crested
cormorants, and Caspian and Forsters terns,
suffer low reproductive rates or produce off-
spring with serious birth defects.
Recognizing that contaminated sediments-
are a problem was a major step. But with that
recognition came the equally important realiza-
tion that no one knew exactly what to do
about the problem. That realization led the U. S.
Congress to authorize a study and demonstra-
tion program on the best ways to assess and
clean up contaminated sediments.
The authorization, contained in the Clean
Water Act of 1987, called upon the Great
Lakes National Program Office (GLNPO) of
the U.S. Environmental Protection Agency to
conduct the project. In 1987, the U.S. and
Canada also ratified a second revision of their
1972 Great Lakes Water Quality Agreement
"(the first revision was in 1978). The document
directs the U.S. EPA to work with its counter-
part, Environment Canada, to establish compat-
ible methods for evaluating sediments, to devel-
op "common methods to quantify the transfer
of contaminants to and from bottom sedi-
ments" and develop a standard approach for
managing the problem, to evaluate existing
clean-up technologies, and to manage long-term
remedial actions.
The EPA response to the congressional
action and the international agreement was to
create a program called ARCS (Assessment
and Remediation of Contaminated Sediments).
The specific aims of the ARCS Program were
to measure concentrations of contaminants at
priority sites on the Great Lakes, to determine
ways of gauging the effects of these concentra-
tions on aquatic life, to recommend ways to
measure risks to wildlife and to human health
posed by the contaminants, and to test tech-
nologies that might be used to clean up the
sediments.
This guide describes the work the ARCS
Program has done and how the knowledge
that has been gained can be applied to areas
where contaminated sediments are causing
environmental degradation.
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Four separate work groups were created to
handle various aspects of the ARCS Program.
TheToxicity/Chemistry Work Group collect-
ed and quantified data on contaminants in sedi-
ments and studied the effects these contami-
nants have on fish and other aquatic life.
The Risk Assessment/Modeling Work Group
studied risks to humans and wildlife created by
existing conditions and compared them to the
risks that would result from various possible
alternatives available for remediating sediment
problems.
StCBOYSAN GRAM) CALUMET BAY ASHTABlilA
mm BWERAND AW RIVER
AND HARBOR RIVER
BUFFALO
iWIR
The Engineering/Technology Work Group
tested and evaluated technologies that might be
used to clean up toxics in sediments.
The Communication/Liaison Work Group
collected and disseminated information to citi-
zens about ARCS and contaminated sediments
and proyided opportunities for citizens to par-
ticipate in the work of the program.
LOCATING THE PROBLEM
The International joint Commission, a binational
body set up by treaty between trie U.S. and
Canada to oversee the Great Lakes and other
boundary waters, has identified 43 heavily pol-
luted harbors, estuaries and tributary rivers on
the five Great Lakes as "Areas of Concern
(AOCs)." Contaminated sediments are consid-
ered to cause major problems in all but one of
these AOCs. Congress directed the ARCS
Program to concentrate its efforts on five of
these areas, two each on Lakes Michigan and
Erie, and one on Lake Huron.
The five are:
The Sheboygan River in Wisconsin: This
river flows into Lake Michigan at the city of-
Sheboygan, Wisconsin. The River is heavily
contaminated with PCBs from industries on its
banks.
The Grand Calumet River and Indiana
Harbor Canal in northwestern Indiana:
Surrounded by major industries, including steel,
chemicals and oil refining, the river and harbor
are heavily polluted with both organic chemi-
cals and heavy metals.
The Saginaw River which flows into Lake
Huron at Bay City, Michigan: Sediments in the
river bottom contain both heavy metals and
PCBs.
The Ashtabula River which, flows into
eastern Lake Erie at Ashtabula, Ohio:The river
is contaminated with heavy metals, PCBs and
other chlorinated organic compounds.
The Buffalo River which flows into Lake
Erie at Buffalo, New York: The river is contami-
nated with complex organic chemicals called
polyniclear aromatic hydrocarbons (RAHs) and
heavy metals.
These five sites contain many different con-
taminants as well as different kinds of bottom
sediments. The Sheboygan River had already
been designated as a National Priority Site by
the Supe'rfund program, as had Fields Brook, a
tributary of the Ashtabula River
DELINEATING THE PROBLEM
Scientists with the ARCS Toxicity/Chemistry
Work Group abbreviated Tox/Chem
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began by compiling lists of likely contaminants
present at each of the sites. This list was created
from information from earlier studies as well as
the historical record of industries located in the
area. These lists helped direct the investigation.
Tox/Chem collected sediment samples from
Indiana Harbor; the Buffalo River and the
Saginaw River. Scientists working with the
Superfund program had already collected sam-
ples from the Sheboygan and Ashtabula rivers.
Using the Research Vessel (R/V)
Mudpuppy a small, shallow draft boat
designed for working in the cramped dimen-
sions of Great Lakes rivers and harbors sci-
entists collected grab samples from the surface
of the sediments. They also collected core sam-
ples that provided a cross-section of sediment
layers extending as much as 20 feet below the
sediment surface. Core samples are essential
because in many cases the most contaminated
sediments lie well below the surface. For exam-
ple, at one location in the Saginaw Riven lying
one foot below the surface of the bottom sedi-
ments, is a layer of black, oily silt containing
concentrations of cadmium, chromium, and
lead three to 15 times greater than that found
in the sands above them. In some cases, highly
contaminated sediments were found as much
as 13 feet below the sediment surface.
Using a satellite-based global positioning sys-
tem (GPS), scientists were able to map with
great precision the locations from which the
samples were taken. Many samples were need-
ed from each site under investigation, in part
because contaminants are usually not evenly dis-
tributed over the bottom. In general, contami-
nants concentrate in fine-grained sediments such
as silts and clays rather than in sand or gravel.
Once the samples gathered by the
Mudpuppy had been analyzed, precise, three-
dimensional maps of the bottom could be
drawn showing where contaminants were con-
centrated.
The Tox/Chem Work Group concluded that
an integrated assessment approach was neces-
sary to measure the seriousness of any contam-
inated sediment problem. An integrated
approach requires the use of a whole group
or "suite" in the scientific jargon of chemical
and biological tests measuring the amounts of
contaminants in the sediments, the bioavai I ability
of these contaminants, and the effects of the
contaminants on living things.
Bioavailability is a-measure of the likelihood
that contaminants will either enter the food
chain or directly affect aquatic organisms rather
than staying tightly bound to the sediments.
Several sediment characteristics have been
identified as having an effect on bioavailability.
For example, higher levels of organic carbon
and acid volatile sulfides in the sediments
reduce bioavailability of some contaminants.
Toxicity-tests measure some of the effects
contaminants have on living things in controlled
laboratory conditions. Various water tests were
performed with whole sediments on what's
called pore water Pore water is held between
the sediment particles and on elutriates which
are created by mixing sediment and pure water
Each of these phases measures a different degree
of availability of contaminants to organisms.
The toxicity tests measured the toxicity of
the sediments by exposing various test organ-
isms both animals and plants to whole
sediments, pore water; or elutriates and studying
the effects of that exposure. For example, tests
were performed on larvae of a small crustacean
called Hyallela azteca. Crustaceans also
include shrimps, lobsters, and crabs. Hyallela
azteca were exposed to whole sediments for
periods ranging from seven to 28 days. At the
end of the test period, the scientists measured
survival, growth and the number of males reach-
ing sexual maturity.
Another test used a small crustacean called
Diporeia (formerly known as Pontoporeia
Lying one foot
below the
surface of
the bottom
sediments
is a layer of
black, oily silt
containing
concentrations
' of cadmium,''
chromium,
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hoyi), an animal that is quite common in the
Great Lakes. This test measured both survival
rates and the extent to which the "pontos," as
they are called, avoided contact with contami-
nated sediments. In 90 percent of the cases,
pontos reacted to contaminants by moving
away from them.
The Toxicity/Chemistry Work Group ulti-
mately decided on a short list of eight bioassay
tests from which two or three should be cho-
sen to measure biological effects.
Scientists also measured the levels of conta-
minants in the tissues of fish caught at the sites,
and they tested sediment samples for muta-
genicity. Mutagenic substances can cause
changes mutations" in genetic material
that can produce tumors or birth defects,
In addition to toxicity and chemistry tests
performed, studies of the animals that actually
lived in and on bottom sediments in the three
areas were also done. The animals of these
benthic communities are often the link
between contaminants in the sediment and the
rest of the food chain. Healthy communities in
clean sediments tend to have far more species
than communities in contaminated sediments.
In some cases, the presence "or absence of par-
ticular species, called indicator species, reveals
the extent of damage to the ecosystem from
contamination. For example, highly.polluted
bottoms like Indiana Harbor may only be pop-
ulated by sludge worms. Sludge worms belong
to a group of animals called oligochaetes. This
group also includes earthworms. They are
adapted to polluted conditions where there is
very little oxygen in the water
Where pollution is a little less severe, the
larvae of some species of midges are part'of
the community, although many of them show
deformities. Cleaner bottoms will have more
species of midges along with mayfly larvae,
various crustaceans and clams. At the three
sites tested by ARCS, sludge worms and
pollution-tolerant midge larva accounted for
90 percent of the total number of species
present. Indiana Harbor had the fewest total
species. Only two midge specimens were
discovered and they were both deformed,
The Buffalo River had the most species. The
survey of the benthic communities showed a
consistent pattern: high pollutant contamination
meant an impoverished community with few
species; and cleaner bottoms supported a
richer more diverse benthos. This result clearly
indicated the ecological effects of contaminated
sediments.
The extensive series of tests conducted by
the Tox/Chem Work Group demonstrated that
contaminants in sediments do indeed affect
both the benthic community and the fish
swimming in the water above contaminated
sediments. Humans eating a lake tout may
ingest toxins that entered the food chain
through a sludge worm's burrowing into sedi-
ments contaminated with PCBs. The question
of risk to humans and to wildlife was examined
by the Risk Assessment/Modeling (RAM) Work
Group, whose work will be described in the
next section.
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Members of the Toxicity/Chemistry Work
Group have prepared a final report called The
ARCS Assessment Guidance Document
that summarizes both what they learned about
assessing the nature and extent of contaminat-
ed sediments and how they learned it The
guidance is for scientists, administrators and
others who have to deal with contaminated
sediment problems. The document offers
detailed instructions on how to gather samples,
analyze their chemical and physical characteris-
tics, and determine the biological effects of
contaminants present in sediments. It compares
how various species react to contaminants in
the sediments and evaluates specific testing
methods. The document also makes specific
recommendations onfwhat tests should be
conducted to evaluate the degree of contami-
nation in sediments, and includes a discussion
on Quality Assurance/Quality Control proce-
dures.
Quality Assurance/Quality Control usu-
ally abbreviated as QA/QC is based on the
recognition that no measurement can be taken
as absolutely exact. The goal of a QA/QC
Program is to enable scientists to establish the
level of uncertainty associated with each set of
data they collect.
KEY FACTS'ABOUT
CONTAMINATED SEDIMENTS
A large number of toxins have been found in
contaminated sediments. These fall into two
categories: metals, such as cadmium, mercury,
.chromium, and lead, and organics, such as
PCBs and PAHs.
Contaminants are typically distributed in a
patchy pattern in sediments.
The physical and chemical nature of the sedi-
ments affects the bioavailability of contami-
nants.
Evaluating the seriousness of any sediment
contaminant concentration requires an inte-
grated sediment assessment approach, includ-
ing tests of the physical and chemical nature
of the sediments and the contaminants as
well as biological tests that measure the
effects of the contaminants on aquatic life.
Contaminants in sediments enter the food
chain in a variety of ways.
The benthic community in contaminated
areas typically contains a less diverse mix of
species than benthic communities in clean
areas. Usual species are those adapted to
polluted conditions.
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lion of risk assessment.
The investigations of the Tox/Chem Work
Group tell us that contaminated sediments
harm the environment They do enter food
chains and eliminate species from the benthic
community. But an answer to the general
question, "Are they harmful?", leads us to some
very specific questions: How much harm? How
much of an effect do the deposits in this place
10
have on the people and animals who live near
them? What remedial action can we take to
gain maximum improvement in the situation at
the least cost?
In the ARCS Program, these questions were
considered by the Risk Assessment and
Modeling (RAM) Work Group. The goal of the
RAM Work Group was to develop and
demonstrate a risk assessment framework that
could identify existing risks to both humans
and wildlife at sites with contaminated sedi-
ments, estimate the impact that various reme-
dial alternatives might have and compare exist-
ing risks with potential risks that could be cre-
ated by remedial action.
To achieve that goal, the RAM Group -
developed a 10-step, standardized process that
could be applied to any contaminated site.
The process is described in a publication called
The ARCS Risk Assessment and
Modeling Overview Document.
The RAM Work Group studied all five
ARCS sites, but it looked most intensively at
the Buffalo and Saginaw rivers. At those two
sites, RAM scientists collected their own sam-
ples of sediment, water and fish to supplement
the information gathered by the Tox/Chem
Work Group: They also studied uses of these
areas by both humans and wildlife in order to
identify pathways of exposure through which
contaminants might reach people or animals,
Alf this data was plugged into the ten-step
framework.
Step one in the ten-step approach is an ini-
tial screening of potential Areas of Concern.
This has already been done for the Great
Lakes by the International joint Commission
through its identification of 43 Areas of
Concern on the lakes 42 of which have sig-
nificant problems with contaminated sediment.
Step two, called Risk Assessment Planning,
begins with the gathering of everything that is
already known about the site, Necessary
information includes physical features, a list of
contaminants likely to be present and the
expected locations of contaminant concentra-
tions. Data about human and'wildlife popula-
tions and the pathways through which they
might be exposed to the contaminants provide
the basis for preliminary estimates of the level
of risk created by the contaminants.
This review of existing information is the
basis for a first approximation of.objectives for
remedial action as well as for the creation of a
short list of possible remediation actions. It also
reveals gaps in essential data that might need
to be filled by additional field work which is
Step Three in the process.
It is a safe generalization to say that the
more we know about a contaminated site the
more certainty there will be in any predictions
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we make about the effects of remedial action.
Of course in real situations our desire for
more information will always run up against
limits in time and, especially, money. Decisions
on how available resources are used have to
be made on a case-by-base~basis. The'Tox/
Chem Work Group has produced an ARCS
Assessment Guidance Document that
describes field1 sampling methods that should
be used to gather data.
Field surveys of the ARCS sites enabled the
RAM Work Group to identify fish consumption
as the most significant pathway between
contaminants in sediments and human beings
at-those sites. Other possible routes include
drinking water and direct exposure from
swimming.
Step four of the process is creation of a
baseline risk assessment. This is an estimate of
the risks to humans and wildlife created by the
existing situation. The baseline assessment
identifies which contaminants and exposure
pathways pose the greatest risk, supports con-
clusions as to whetherTemediation is needed,
and provides a standard for evaluating the
effectiveness of any action taken.
Step five is the ranking of subareas within
the Area of Concern. Contaminants are
typically distributed unevenly over the bottom.
Mapping their distribution allows us to desig-
nate hot spots which might be priority areas-
for clean up.
Step six is the screening of possible remedi-
al alternatives. The idea is to eliminate courses
of action that obviously cannot be used at the
site and to reveal gaps in information that
would need to be filled by further field testing
before any remedial action could be under-
taken.
Step seven uses a technique called mass
balance modeling to trace the fate of contami-
nants entering an area of concern, The quanti-
ties of contaminants coming into a system are
called "loadings." Once these toxic loadings
reach the water; any of several things can hap-
pen to them. If they sink to the bottom, they
may be stored in sediments or they may enter
the food chain in the bodies of benthic animals.
If something the propeller of a passing ship,
storm waves, the thrashing of spawning carp
lifts them out of the mud and into the
water, they may enter the food chain through
the bodies of free-swimming organisms. They
may be transformed or degraded into other,
perhaps less harmful, substances. Or they may
be transported out of the system from the
Saginaw Riven for example, into Saginaw Bay.
To create a mass balance model, scientists
plug information gathered on the actual distrib-
ution of contaminants in the system into sets
of equations that create a mathematical model
of that system. The computer model simulates
the physical movement of water; sediment and
contaminants in the system as well as the
movement of contaminants in the food chain.
With mass balance modeling, we can estimate
the likelihood that humans and wildlife are
being exposed to contaminants from sediment
at levels that are known to be harmful.
The results produced by the computerized
models are combined with all the other infor-
mation gathered from the site to provide the
data needed for step eight, the comparative
risk assessment. This assessment gives us the
most precise information we can get about the
results that are likely to follow from various
courses of action.
For example, if we reduce loa'dings to zero,
that is, stop all discharges of a particular
contaminant, will we see a quick decline in
concentrations of that chemical in the system?
Or is the outflow from the system so slow that
it would take years for the contaminants now
in the system to be flushed out?
What about the contaminants already pre-
sent in the sediments? Suppose we just leave
What about
the contami-
nants already
present in the
sediments?
Suppose we
just leave
them where
they are., ,
What kind
wouId they
-------
What
remediation
method will
give us the
greatest
improvements
for the
money spent
or reduce
undesirable
side effects to
a minimum?
f --). '
them where they are. What kind of effect
would they have on the environment five, ten
or .twenty years into the future?
Suppose we carefully map the bottom of
the Ashtabula or the Buffalo or any other Area
of Concern and just dredge the nastiest of the
hot spots, the places with the highest concen-
trations of contaminants. Would that remove
enough contaminants to produce a major
improvement in the richness and diversity of
the benthic community? Would it lead to signif-
icant declines in contaminant levels in fish tis-
sues?
Would the improvement be greater if we
dredged the entire bottom? Would the differ-
ence be sufficient to justify the additional
expense? What remediation method will give
us the greatest improvements for the money
spent or reduce undesirable side effects to a
minimum?
Step nine is the selection of a final remedial
alternative. The choice here is based on the
information gathered so far; on predictions gen-
erated by the mass balance model, and on
political and economic factors. The ARCS
Program gathered the information needed to
make this selection, but it did not actually
decide on plans for the sites studied, leaving
those decisions to the stakeholders in each
AOC.
Once remedial action has been taken, step
ten requires the continued monitoring of the
site to determine if the action has had the
desired effect.
With all of this information available,
Remedial Action Plan (RAP) Teams can make
informed, scientifically defensible decisions as to
the optimal remedial actions.
12
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The ARCS Engineering/Technology Work
Group concerned itself with what we do after
we discover that a body of sediments is conta-
minated and that the contamination creates a
significant hazard.
Developing a plan for remediating a contami-
nated sediment situation involves a long series of
choices. Should the sediments be left where
they are but somehow isolated from the envi-
ronment? If they must be dredged, what method
should be used? Will aljJJne sediments containing
contaminants be removed, or will efforts be
concentrated only on the hottest of the hot
spots? How are the dredged sediments to be
transported? If they are to be treated, which
method should be used?
Several factors have to be taken into
account in making these decisions. The most
important include:
I. The location of the sediments. Are
they in a busy shipping lane that must be
dredged periodically to maintain the depths
needed for navigation, or are they in untrav-
eled.waters where maintenance dredging is
not required? Are they in open waters, or in
tight corners, up against docks or other struc-
tures where some kinds of dredges could not
maneuver? Can equipment be placed on the
nearest shores or is this land inaccessible or
otherwise unsuitable for such use?
2. The extent of the contaminated
deposit. Is it confined to a small area, or is
it spread along four miles of river channel? Is
it confined to the topmost layers of sediment,
or does it extend deep into the bottom
deposits? Will a clean up require the removal
of 10,000 cubic yards of material or500,000?
3. What is down there with it? The bot-
toms of many harbors are littered with
everything from shopping carts to old cars.
The presence of such debris influences the
choice of dredging methods.
4. What contaminants are present?
Treatment methods are designed to handle
specific classes of contaminants, for example,
metals or chlorinated compounds. Some
heavily contaminated sediments might
require two or more treatments to remove
all the problem materials.
5. How available are the various kinds
of equipment and technology that
might be used in a remedial action?
For example, clamshell dredges are widely
used and widely available, but some types of
specialty hydraulic dredges are quite rare
and may not be accessible without a long
wait. Similar problems can arise with the
equipment needed for various treatment
technologies.
6. How much money is available? In most
situations, this is the biggest question of all,
Treating sediments to remove or neutralize
contaminants is expensive. And the more
material that needs dredging or treatment,
the more expensive the operation.
The rest of this section will be devoted to
discussion of the various technologies available
to reduce or eliminate the.hazards created by
contaminated sediments. We will describe the
situation as of mid-1994. But things are changing
fast in this area. New technologies are being
introduced regularly while other ideas, once
thought promising, are being dropped.
Howeven through all these changes, the
broad categories are likely to remain the same.
New dredging tools may be developed, but
they will probably all fall within the categories
of mechanical or hydraulic. New treatments
will most likely be new versions of such exist-
ing forms as solvent extraction or bioremedia-
tion. So while this guide cannot keep you up-
to-date on each new development, it can pro-
vide you with a framework for understanding
innovations as they come along.
New
technologies
are being
introduced
regularly while
other ideas,
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The first decision that has to be made in
developing a remedial design is whether the
hazards can be sufficiently reduced with the
material left in place in situ, to use the
Latin term favored by scientists or if the
sediments must be removed by dredging.
NON-REMOVAL TECHNOLOGIES
The use of Non-Removal Technologies is feasi-
ble only if dredging is not required for naviga-
tion reasons and if the contaminated area is in
. waters where storms or other disturbances
will not wash away capping material. The
choices are:
I. Capping. Material is placed on top of the
contaminated sediments. The simplest and
cheapest caps are such materials as sand,
gravel or clean sediment. The cap must be
thick enough to prevent benthic organisms
from burrowing into the contaminated layers
and to effectively prevent the loss of conta-
minants from the sediments through the cap
and into the water More expensive caps
may use special materials called geotextiles.
In the Sheboygan River in Wisconsin, several
small areas heavily contaminated with PCBs
have been capped with alternating layers of
gravel and geotextiles topped with a layer of
larger rocks called cobbles. The total area
covered is 20,000 square feet, the equivalent
of a square about 140 feet on each side.
2. Containment. This method isolates a por-
tion of a waterway by enclosing it within cof-
ferdams, dikes or other structures. In
Waikegan Harbor in Southern Lake Michigan,
a boat slip was walled off in this way, additional
contaminated sediments were placed inside
the walls, and the whole thing was then
capped like a hazardous waste landfill.
3. Treatment in situ. Chemicals are applied
' to the sediment to destroy the contaminants.
At this point, this is a possibility not a practical
alternative. It is very difficult to be sure that all
the contaminated material has been treated.
The uncertainty is greatest for the deepest
sediments, and they may be the most contam-
inated. "Overtreatment," that is, applying
more chemicals and covering a larger area
than the contaminated zone is a possible
answer to this problem, but overtreatment
raises costs. Releasing the treating chemicals
into the waterway can also cause problems.
4. Immobilization in situ. Also called solidi-
fication or stabilization, this involves mixing
cements or other materials into the sediments
to alter their physical and chemical make up
so that contaminants cannot escape, The
solidifying materials must be tested in the
laboratory on the specific sediments to be
treated before each individual attempt to use
this method.
Part of the cost of in situ methods espe-
cially of capping and isolating lies in the
continuing monitoring that must be done to
make sure that the caps, dikes or cofferdams
are still working.
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Until recently, dredging was a job done solely
to keep channels and harbors deep enough for
boats or ships. The goa was to get the work
done as quickly and cheaply as possible. If sedi-
ments escaped from the dredge and drifted
off, the only concern was whether they came
to rest somewhere out of the way.
Environmental dredging is very different
from traditional navigational dredging of uncon-
taminated sediments. In environmental dredg-
ing, resuspension of sediments and their
associated contaminants must be carefully
controlled. If we lift contaminants from the
bottom only to scatter them through the
water, the dredging could do more harm than
good. Environmental dredging may require the
use of barriers such as oil booms, which sit on
the water surface, or silt screens and silt cur-
tains, which extend from the surface to the
bottom to confine resuspended sediments.
Concerns about resuspension have also stimu-
lated the creation of new dredge designs
which will be discussed below.
The sudden release of contaminants into
the water that may accompany dredging has to
be taken into consideration in any decision to
dredge a particular site. However; the harm this
sudden influx of contamination may do has to
be balanced against the damage that can be
done by a slow, gradual release of toxics that
extends over many years as the sediments
remain in place,
MECHANICAL DREDGES
The bucket or clamshell dredge is the most
widely used* dredge in the Great Lakes. Its two
hinged halves are opened wide and then
dropped onto the bottom where they sink
into the sediment. The operator then raises
the dredge, causing the halves to swing togeth-
er; enclosing a load of sediment. The closed
bucket is then raised above the water; swung
over a barge, and opened, allowing the sedi-
ment to drop onto the barge.
Bucket dredges are excellent for use in
close quarters, such as around docks or break-
waters. Their main disadvantage is that sedi-
ment can spill out of the top of the bucket as ,
it is raised. The watertight bucket, originat-
ed by the Japanese but now manufactured by
U.S. firms as well, uses covers on top of the
bucket to minimize spillage. Typical designs also
use rubber gaskets, tongue-in-groove joints or .
a "matchbox" design to make the buckets
more watertight One design removes sedi-
ment in layers, leaving a flat sediment surface.
Backhoes, which are mainly used for
excavations on land, can be used in water if
sediments are in shallow water very near the
shore. Other types of mechanical dredges,
among them bucket ladders, dippers and
draglines, create far too much resuspension to
be usable for contaminated sediments.
HYDRAULIC DREDGES
In essence, hydraulic dredges are enormous
vacuum cleaners that simply suck sediments
from the bottom. They may be equipped with
rotating blades, augers or high-pressure water
jets to loosen the sediment. The most common
type used in the U.S. is called a cutterhead.
It uses rotating blades to loosen sediments.
Rotating augers are, in effect, large drills
which not only loosen the sediments but also
pull them into the dredge. Equipment such as
sediment shields and gas collection systems can
be added to these dredges to reduce resus-
pension of sediment or the escape of volatile
contaminants into the water
Hydraulic dredges have a very high capacity
that is, they can remove a large volume of
material in a short time. However; their pumps
pull in a lot of water with the sediment.
Dredged materials pulled up by mechanical
dredges are typically about half water and half
solids by weight. Hydraulic dredges bring up a
Until recently,
dredging was
a job done
solely to keep
channels and
harbors deep
enough for
boats or ships.
The goal was
to get the
work done as
quickly said
cheaply as ,
possible. If .
15
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slurry that is likely to be 80 to 90 percent
.water and just 10 to 20 percent solids. This
means that if you remove a given quantity of
sediment with a hydraulic dredge you will have
a much larger volume of material to transport,
store or treat. Larger volumes usually mean
more expense and greater potential for conta-
minants to be released during processing of
the dredged material.
Debris is also a problem with hydraulic
dredges. Cutterheads can break up some large
pieces, but in general, any debris larger than
the suction pipe cannot be removed with
hydraulic equipment.
PRETREATMENTAND STORAGE
Once we have removed contaminated sedi-
ment from a waterway, we have to decide
what to do with it. The U.S. Army Corps of
Engineers began using confined disposal facili-
ties (CDFs) to contain contaminated dredged
materials in the Great Lakes in the early 1970s.
They have provided a way to isolate sediments
and the contaminants they contain.
CDFs must be big enough to hold large
quantities of dredged sediments. Even at very
hazardous concentration levels, contaminants
amount to only a very small fraction of the
mass of those sediments, When we use CDFs,
we are building and maintaining a home for
thousands of pounds of sediments for every
pound of toxic material we isolate.
Pretreatment may be needed to remove
large pieces of debris from dredged sediments
or to separate sediment particles into relatively
uniform size fractions so they can be treated
effectively. Dewatenng may also be necessary
to reduce the volume of material requiring
treatment or storage. Technologies used for
producing a uniform particle size are well
established in the mining industry. Dewatering
methods have been taken from the processes
used to treat municipal waste water
CDFs can be used for the temporary stor-
age of sediments awaiting treatment Many
treatment methods are quite slow. It could
take years to treat all the contaminated sedi-
ment in one'harbor. By using a CDF, we can
get dredging done quickly and efficiently,
removing contaminants from the environment
with minimum interference from navigation
and at the lowest possible cost. Then we can
treat the sediments at the CDF
16
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The need to find ways to clean up our environ-
mental problems has inspired research into a
broad range of technological methods for
either removing contaminants from soil or sedi-
ment, or breaking them down into harmless
components. Some of these technologies are
ready for use in full-scale field operations.
Others have been tested only in laboratories.
In this section, we will provide a brief overview
of the present state of sediment treatment.
THERMAL DESTRUCTION
TECHNOLOGIES
"Thermal destruction'^is a fancy way of saying
that these processes use heat to destroy cont-
aminants. Heat is used mainly against organic-
contaminants such as PCBs, PAHs, dioxins and
furans, petroleum hydrocarbons, and pesticides.
Organic contaminants are compounds with
their major components being such innocuous
elements as carbon, oxygen and hydrogen.
Their toxicity is a result of the specific ways
these elements are combined. Heat can sever
the chemical bonds that hold the compounds
together; rendering them less toxic. Examples
of thermal destruction technologies are incin-
eration, pyrolysis and supercritical oxidation.
THERMAL DESORPTION
TECHNOLOGIES
These technologies use heat not to destroy
contaminants but to separate them from the
sediments. Sufficient heat is applied to vapor-
ize water, organic compounds and some
volatile metals. These can then be destroyed in
an afterburner or collected as liquid for further
treatment. A thermal desorption technology
was demonstrated on a pilot-scale by the
ARCS program at the Buffalo and Ashtabula
Rivers. It achieved removal efficiencies up to
96 percent for PAHs from the Buffalo and up
to 97 percent for PCBs from the Ashtabula.
Advantages of thermal desorption over
thermal destruction include lower energy
requirements because lower temperatures are
used and emissions are reduced, and it is less
likely that toxic compounds will be formed by
this process. There is also no need to add
other chemicals to the sediments to make the
process work.
Disadvantages include the need for an addi-
tional destruction process for the vaporized
compounds and lower effectiveness with the
less readily vaporized organic compounds.
IMMOBILIZATION TECHNOLOGIES
Sediments can be solidified by adding cements,
thermoplastics or other materials. They can also
be chemically stabilized by adding substances
that bind contaminants and keep them in-place.
Heat can immobilize contaminants through
a process called vitnfication:This process uses
very high temperatures (up to 2900 degrees
F.) to convert contaminated soils or sediments
into a glass-like substance that is strongly resis-
tant to leaching. In addition to immobilizing
contaminants, this process also destroys some
organic compounds. A small scale demonstra-
tion of this process was conducted with sedi-
ments from the New Bedford Harbor
Superfund site in Massachusetts.
17
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Bacteria have
long been
used to treat
sewage and
industrial
waste waters,
and recently
^ they -have
SOLVENT EXTRACTION
TECHNOLOGIES
Chemical solvents can be added to sediments
to separate contaminants from particles and
water that make up the bulk of the material.
Once the contaminants have been separated,
they can be subjected to further treatment.
By separating the contaminants before further
treatment, the amount of material that needs
to be treated can be reduced by as much as
20 times.
Solvent extraction could be used mainly to
deal with organic contaminants such as PCBs
and petroleum hydrocarbons, although some
heavy metals can be removed with acidic solu-
tions.
One solvent extraction process, the Basic
Extractive Sludge Treatment process (B.E.S.T.)
was demonstrated on a pilot-scale by the
ARCS Program with sediments from the
Grand Calumet River The process achieved a
better than 96 percent removal rate for both
PCBs and PAHs.
CHEMICAL TREATMENT
TECHNOLOGIES
These use special chemicals called reagents
added to sediment to destroy contaminants.
Heat can also be used to accelerate the chem-
ical reactions. Examples of these processes are
the Base Catalyzed Decomposition (BCD)
process and the Ecologic process, both of
which were tested on a bench-scale by the
ARCS Program.
BIOREMEDIATION
Bacteria have long been used to treat sewage
and industrial waste waters, and recently they
have been applied to the treatment of organic
compounds in soils, sediments and sludges.
The ARCS Program participated in a pilot-
scale test of bioremediation on PCB-laden sed-
iments from the Sheboygan River in Wisconsin.
Bacteria are known to be able to break
down PCBs, but the question of whether biore-
mediation is a practical method of dealing with
this group of chemicals is still very much open.
SEDIMENT WASH ING
This is an adaptation of technology that has
long been used in mining and mineral process-
ing to separate solids suspended in water into
sets of different sized particles. It was demon-
stratec by the ARCS Program on a pilot-scale
with 300 cubic yards of sediment dredged
from the Saginaw River Sediments in the
Saginaw are mostly sand, but the contaminants
are concentrated in the finer particles, the silts
and clays that are mixed with the sand. By sep-
arating silts and,days from the sands, the
process can substantially reduce the amount of
material that needs to be treated. At Saginaw,
80 percent of the material fed into the process
emerged as sand clean enough to be used for
beneficial purposes such as beach nourishment.
The remaining 20 percent, the finer particles,
contained the contaminants and could be
treated further by one of the previously dis- .
cussed technologies.
Things are happening fast in the field of
remediation technology. Anyone interested in
keeping up-to-date on developments in this
dynamic field should look at fhe databases
prepared by Environment Canada and the U.S.
EPA. The Canadian database, called SEDTEC is
available from WastewaterTechnology Centre,
867 Lakeshore Road, Burlington, Ontario,
Canada, L7R 4L7. The U.S. databasej called
VISITT is available from PRC Environmental
Management, Inc.,
VA 22102.
505 PRC Drive, McLean,
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The ARCS Program was conducted with the
Great Lakes ecosystem as its specific laboratory,
but the issues raised and the problem-solving
strategies considered are increasingly relevant
nationwide.
Wherever you live, there is likely to be a
lake or a stream that has been under long-term
or periodic stress from contaminants dumped
from the end of a factory waste stream, a farm
field or city street, a hazardous waste dump, or
settling out of the sky from smokestacks. Many'
of these contaminants lodge in sediments where
they are gradually re-exposed to the environ-
ment and continue to cause damage over a
period of many years.
With new information on assessment and
treatment available from the ARCS Program,
other public and private research, new knowl-
edge about the extent of contaminated sedi-
ment and its effect on wildlife and people,
many new opportunities will arise for clean-up.
Some of this clean-up will stilf be expensive,
however Strong public involvement will be
necessary to ensure that the long-term eco-
nomic and environmental benefits of contami-
nated aquatic land rec amation are considered
along with the costs of failing to take action.
Citizens can also play a role in shaping con-
taminated sediment clean-up plans for their
areas by asking questions that will elicit specrfic
responses from researchers about methodolo-
gies and hoped-for results. Questions devel-'
oped by citizens active in the ARCS
Communication/Liaison Work Group in
response to remediation efforts at the five
ARCS sites may also be relevant in other loca-
tions. They include the following:
I. Has any testing been done to find out
whether this sediment is contaminated?
What chemicals did the researchers look for?
On what basis did they make these choices?
Was biological testing done?
2. What kind of sampling was done? Were
"grab" samples done or was a core taken?
Was the core homogenized before being
analyzed or was it analyzed in separate layers?
How deep was each layer? How deep was
the whole core? How deep is unconsolidated
material thought to go at this site? How
much of that do you think is likely to show
anthropogenic effects (human-caused mess)?
3. If testing has been done, what contaminants
were found? Are there both organic com-
pounds and heavy metals? Are any of them
persistent toxic compounds that are likely to
build up in the fatty tissue or muscle offish
or other organisms?
4. What is the physical makeup of sediment at
this site (proportion of clay, silt, sand, for
instance)? Contaminants don't bind to sand
and so will escape through the water col-
umn. They bind most strongly to clay and silt
and so can be captured by sediment dredg-
ing, disposal and treatment.
5. What disposal options are being considered?
On what basis? Short-term economic con-
cerns only or long-term protection that will
limit future liability problems?
19
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Strong public
involvement
will be
necessary to
ensure that
the long-term
economic and
environmental
contaminated
6. Will dredging be limited to a navigation
channel or (in the case of a river or other
stream as opposed to open ocean or big
lake) will the slopes on either side of the
channel be dredged as well to prevent
recontamination? Are there high levels of
contaminated sediments farther upstream
than the proposed site to be dredged? What
is your strategy for preventing recontamina-
tion from upstream sediments moving down
to cover the dredged area? '
7. Is your remediation plan linked to pollution
prevention of active sources?
8. What before and after monitoring is planned
both for dredging activities and for storage?
9. Is any habitat restoration proposed in con-
cert with the sediment removal or as mit-
, igation for the loss of habitat to be caused
by the dredging and disposal operation?
10. Have you mapped priority hot spots for
clean-up within the overall area to be
remediated?
I I. Have you considered the impact of sedi-
ment resuspension during dredging and
wbat safeguards are in place for minimizing
their impact?
Meaningful public involvement in the plan-
ning and decision-making stages will continue
to be important in efforts to remediate
contaminated sediment sites.
ARCS
INFORMATION LIBRARIES
Buffalo, NY Buffalo and Erie County
Public Library, Science Department, Lafayette
Square, Buffalo, NY 14203, (716) 858-7101;
J.R Dudley Branch Library, 2010 South Park
Avenue, Buffalo, NY 14220, (716) 823-1858;
Great Lakes United, Cassety Hall, State
University at Buffalo, 1300 Elmwood Avenue,
Buffalo, NY 14222, (716) 886-0142.
Indiana Harbor Canal/Grand Calumet
River, IN Gary Public Library, 220 W. 5th
Street, Gary, IN 46402, (219) 886-2484; East
Chicago Public Library, 2401 East Columbus
Drive, East Chicago, IN 46312, (219) 397-2453;
Reference Library, Indiana University NW, 3400
Broadway, Gary, IN 46408, (219) 980-6580.
Saginaw River, Ml Hoyt Library, Michigan
Room, 505 James Street, Saginaw, Ml 48605,
(517) 755-0904; Bay City Branch Library, 708
Center Bay City, Ml 48708, (517) 893-9566.
Shebeygan River,Wl Mead Public
Library, 710 Plaza 8, Sheboygan, Wl 53081,
(414)459-3432.
Ashtabula River, OH Ashtabula County
District Library, 335 W. 44th, Ashtabula, OH
44004, (216) 997-9341.
Additional Repositories Library, Great
Lakes National Program Office (GLNPO),
USEPA, 77 W. Jackson Blvd., Chicago, L 60604.
International Joint Commission Library
University of Windsor; Windsor; Ontario N9A
6T3, (519) 973-7023.
For more information about the U.S.
EPA's ARCS program, call the EPA Hotline:
I -800-621 -8431 or write ARCS, Great Lakes
National Program Office, U.S. Environmental
Protection Agency, 77 W. Jackson Blvd.,
Chicago, IL 60604.
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