United States
Environmental Protection
Agency
Office of
Research and Development
Washington DC 20460
EPA/625/6-91/028
April 1991
&EPA Handbook
Remediation of
Contaminated Sediments
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Handbook
Remediation of
Contaminated Sediments
EPA/625/6-91/028
April 1991
Center for Environmental Research Information
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Printed on Recycled Paper
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TABLE OF CONTENTS
Page
LIST OF TABLES iv
LIST OF FIGURES iv
ACRONYMS v
ACKNOWLEDGEMENTS vi
PREFACE vii
1 PHYSICAL AND CHEMICAL CHARACTERISTICS OF SEDIMENTS 1
1.1 Introduction 1
1.2 Properties of Sediments Affecting Contaminants 2
1.3 Forms and Reactions of Contaminants 2
1.4 References 4
2 SEDIMENT TOXICITY ASSESSMENT 5
2.1 Introduction 5
2.2 Environmental Regulations that Relate to Contaminated Sediments 5
2.3 Current Development of Sediment Assessment Tools 7
2.4 References , 9
3 PROCEDURES FOR CHARACTERIZATION OF CONTAMINATED SEDIMENTS 11
3.1 Introduction 11
3.2 Sampling Plan 11
3.3 Sampling Methods 12
3.4 Physical and Chemical Analyses 13
3.5 Modeling Sediment Transport and Contaminant Fate and Transport 13
3.6 References 14
4 REMOVAL AND TRANSPORT 15
4.1 Introduction 15
4.2 Removal 15
4.3 Transport 18
4.4 Compatibility with Downstream Processing 18
4.5 References 18
5 PRE-TREATMENT '. 21
5.1 Introduction : 21
5.2 Slurry Injection : ." , 21
5.3 Dewatering 22
5.4 Particle Classification 24
5.5 Handling/Rehandling 24
5.6 References 25
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TREATMENT TECHNOLOGIES
6.1 Introduction
6.2 Technology Screening Logic
6.3 Extraction Technologies
6.4 Destruction/Conversion
6.5 Containment
6.6 References ..
27
27
.. 27
30
•ao
Qfi
38
DISPOSAL
7.1 Introduction .......
7.2 Capping ,
7.3 Confined Disposal Facility (CDF).
7.4 Landfills
7.5 References ,
.41
.41
.41
.43
.43
.43
in
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LIST OF TABLES
Page
1-1 Availability of Metals in Common Chemical Forms 3
1-2 Typical Fate of Potentially Available Metals in a Changing Chemical Environment 3
2-1 Sediment Quality Assessment Methods 8
4-1 Comparison of Hydraulic and Mechanical Dredges 16
4-2 Comparison of Selected Mechanical Dredges 16
4-3 Comparison of Selected Hydraulic Dredges 17
4-4 Comparison of Selected Pneumatic Dredges 18
4-5 Controls for Transport Options 19
5-1 Summary of Dewatering Techniques 23
5-2 Summary of Sediment/Water Separation Techniques .....25
6-1 Identification of Hazardous Waste Treatment Technologies Considered
forthe Treatment of New Bedford Harbor Sediments 28
6-2 Demonstration Test Results of CF Systems Organic Extraction Process 31
LIST OF FIGURES
Page
6-1 CF Systems Organic Extraction Process 30
6-2 BEST Chemical Extraction Process 31
6-3 Low Temperature Thermal Stripping 32
7-1 Schematic of Capping Options 42
IV
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ACRONYMS
AET Apparent Effects Threshold
ANSI American National Standards Institute
ARAR Applicable or Relevant and Appropriate Regulation
ARCS Assessment and Remediation of Contaminated Sediments
BEST Basic Extraction Sludge Treatment
CAA Clean Air Act
CAD Contained Aquatic Disposal
CDF Confined Disposal Facility
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CSD Criteria and Standards Division
CWA Clean Water Act
DOD Department of Defense
EIS Environmental Impact Statement
EP Extraction Process
EPA Environmental Protection Agency
EqP Equilibrium Partitioning
ERL Environmental Research Laboratory
FIFRA Federal Insecticide, Fungicide, and Rodenticide Act
GLNPO Great Lakes National Program Office
GLWQA Great Lakes Water Quality Agreement
1SV In Situ Vitrification
LEEP Low Energy Extraction Process
LTTS Low Temperature Thermal Stripping
MPRSA Marine Protection, Research, and Sanctuaries Act
NEP National Estuary Program
NEPA National Environmental Policy Act
NETAC National Effluent Toxicity Assessment Center
NPDES National Pollutant Discharge Elimination System
NPL National Priorities List
OERR Office of Emergency and Remedial Response (Superfund)
OMEP Office of Marine and Estuarine Protection
QAPP Quality Assurance Program Plan
PAH Polycyclic Aromatic Hydrocarbon
PCB Polychlorinated Biphenyl
RCRA Resource Conservation and Recovery Act
RHA Rivers and Harbors Act
ROV Remote Operated Vehicle
SAB Science Advisory Board
SARA Superfund Amendments and Reauthorization Act
SBLT Standard Batch Leachate Test
SITE Superfund Innovative Technology Evaluation
SLT Standard Leachate Test
SQC Sediment Quality Criteria
TCLP Toxicity Characteristic Leaching Procedure
TEA Triethylamine
TIE Toxicity Identification Evaluation
TSCA Toxic Substances Control Act
UCS Unconfined Compressive Strength
USAGE United States Army Corps of Engineers
USEPA United States Environmental Protection Agency
USFWS United States Fish and Wildlife Service
VOC Volatile Organic Compound
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ACKNOWLEDGEMENTS
This document is a compilation of material applicable to the remediation of sites that contain contaminated sediments.
The information was compiled by Mr. Timothy Voskuil of EQUITY ASSOCIATES, Inc., Knoxville, Tennessee underthe
technical direction of Mr. Ed Barth of the Center for Environmental Research Information, Cincinnati, Ohio. Dr. Carol
Bass of the Office of Emergency Response, Washington, D.C. provided program office input. Many individuals
contributed to the preparation and review of this document; a partial listing appears below.
Development of Material
Physical and Chemical Characteristics of Sediments
Dr. Robert P. Gambrell, Louisiana State University, Baton Rouge, Louisiana.
Dr. William H. Patrick, Louisiana State University, Baton Rouge, Louisiana.
Sediment Toxicity Methods
Dr. Carol Bass, USEPA, Office of Emergency Response, Washington, D.C.
Mr. Chris Zarba, USEPA, Office of Water, Washington, D.C.
Procedures for Characterization of Contaminated Sediments
Dr. Steve McCutcheon, USEPA, Environmental Research Laboratory, Athens, Georgia
Mr. Jan Miller, USAGE, Chicago, Illinois
Removal and Transport
Mr. Jan Miller, USAGE, Chicago, Illinois
Pre-Treatment ,
Mr. Daniel Averett, USAGE, Waterways Experimental Station, Vicksburg, Mississippi
Treatment Technologies
Mr. Daniel Averett, USAGE, Waterways Experiment Station, Vicksburg, Mississippi
Mr. Ed Barth, USEPA, Center for Environmental Research Information, Cincinnati, Ohio
Mr. Rich Griffiths, Risk Reduction Emergency Laboratory, Edison, New Jersey
Dr. George Hyfantis, International Waste Management Systems, Knoxville, Tennessee
Mr. Tommy Meyers, USAGE, Waterways Experiment Station, Vicksburg, Mississippi
Dr. Gary Sayler, Center for Environmental Biotechnology, University of Tennessee, Knoxville,
Tennessee
Mr. Dennis Timberlake, USEPA, Risk Reduction Laboratory, Cincinnati, Ohio
Disposal
Mr. Jan Miller, USAGE, Chicago, Illinois
Technical Reviewers
Mr. Joe Corrado, Malcolm Pirnie, Inc., White Plains, NY
Mr. Merten Hinsenveld, Fellow-North Atlantic Treaty Organization/Committee for Challenges of
Modern Society (for the Netherlands)
Mr. Mike Kravitz, USEPA, Office of Water Regulations and Standards, Washington, D.C.
vi
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PREFACE
Contaminated sediments may pose risks to both human and environmental health. Such sediments may be found in
large sites, such as the harbors of industrialized ports. However, they are also frequently found in smaller sites, such
as streams, lakes, bayous, and rivers. In response to the risk that contaminated sediments pose, new methods for the
remediation of contaminated sediment problems have developed rapidly during the last few years. Remediation options
include no action (monitored natural attenuation), removal, treatment, and containment. All areas of contaminated
sediment remediation have seen considerable development, especially technologies for the treatment of contaminated
sediments.
This handbook focuses on small site contaminated sediments remediation with particular emphasis on treatment
technologies. It is designed to provide a succinct resource booklet for government regulatory personnel, permit writers,
remedial project managers, environmental scientists and engineers, plant owner/operators, environmental consultants,
and other individuals with responsibilities for the management of contaminated sediments.
The handbook is organized to address the major concerns facing contaminated sediment remediation. Chapter I
describes the physical and chemical characteristics of sediment, with special emphasis on ways in which sediment
property changes affect contaminant mobility. Chapter II addresses sediment toxicity assessment and describes the
current status of the EPA effort to address this important topic. Chapter III discusses sampling techniques and analytical
and modeling methods used to characterize contaminated sediments. Chapter IV describes removal and transport
options. Chapter V presents pre-treatment technologies. Chapter VI, the primary focus of this handbook, describes
four major classes of treatment technologies. This chapter offers a comprehensive overview of specific treatment
technologies and addresses applicability, limitations, and demonstrated results; it also presents references for further
information. Finally, Chapter VII reviews disposal alternatives for contaminated sediments that are not treated.
VII
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CHAPTER 1
PHYSICAL AND CHEMICAL CHARACTERISTICS OF SEDIMENTS
1.1 Introduction
Sediment is the material that settles to the bottom of any
body of water. Its primary components are interstitial
water and soil particles. Interstitial water can comprise up
to 90 percent of the total volume of unconsolidated, top
sediment horizons and close to 50 percent of deeper,
more compacted sediments. Soil particles found in sedi-
ments are derived from surface erosion of soils in the
watershed, bank erosion, and redistribution of the bed
load in waterways. Sediments vary widely in particle size
distribution and are generally finer in texture than their
source soils. Segregation of particle size occurs within
the water body as a result of currents such that the smaller
particles accumulate in quiescent zones and coarser
particles are found where the current is greater. Organic
matter, another important component of sediment, may
range from near zero to greater than 10 percent of the
sediment solid phase. Minor (but not necessarily unim-
portant) components of sediments include shells and
other animal parts, plant detritus, sewage/and industrial
wastes such as metals, other inorganic chemicals, syn-
thetic organic compounds, and oil and grease.
Sediments are a very important part of aquatic ecosys-
tems and in and of themselves should not be considered
a problem. They can become problematic in at least three
ways: excessive sedimentation due to human activity
(erosion from agriculture or construction, etc.) can blanket
the bottom of aquatic ecosystems and cause environ-
mental damage in a number of ways; excessive sedimen-
tation in areas of human commerce can disrupt shipping
and require maintenance dredging; and contaminants
can accumulate in sediments to the point where they
endanger human and/or ecosystem health. This third
type of problem is the focus of this document.
Sediments are considered contaminated when anthropo-
genic sources of pollution exist in high enough concentra-
tions and are sufficiently available to affect human and/or
ecosystem health. Contaminated sediments threaten
human health when humans drink water contaminated by
contact with sediments, eat organisms (such as fish and
shellfish) contaminated through bioaccumulation in the
food chain, or come in direct dermal contact with contami-
nated sediments. Contaminants impact ecosystems by
increasing the mortality rates and/or by decreasing the
growth or reproductive rates of susceptible populations.
These impacts can be transferred throughout the ecosys-
tem via food chain links and other ecological mecha-
nisms.
Contaminants enter the water body from point sources
(such as municipal and industrial effluents), non-point
sources (such as agricultural and urban runoff), and other
sources (such as spills, leaks, and dumping of wastes). A
portion of the contaminants may then settle in the sedi-
ments. Common contaminants of concern include halo-
genated hydrocarbons (PCBs, dioxins, many pesticides,
etc.), polycyclic aromatic hydrocarbons (PAHs such as
naphthalene, pyrenes, etc.), and other organics (such as
benzene), as well as metals (including iron, manganese,
lead, cadmium, and mercury). Although many of the
organic contaminants do degrade with time, the rates of
degradation are generally slow and these chemicals tend
to remain in the sediments for long periods of time, thus
increasing their impact on the environment. Metals, as
elements, do not degrade.
The physical and chemical characteristics of sediments
exert a great deal of influence upon, the bioavailability of
sediment contaminants. These characteristics vary greatly
from site to site. As a result, site characteristics should
impact remediation decisions. This chapter reviews
sediment characteristics to evaluate when selecting from
among remediation alternatives. These alternatives in-
clude no action, treatment, containment, and disposal.
Important physical and chemical changes may occur in
contaminated sediments during their removal, handling,
transport, treatment, and disposal. Important factors to
consider during this selection process include the
following:1
1. Nature and magnitude of the contamination.
2. Chemical and physical properties of the sediment.
3. Remediation alternatives potentially available.
4. Behavior of the contaminant(s) under different reme-
diation alternatives.
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5. Potential changes in the physical and/or chemical
properties of sediments under different remediation
alternatives.
6. Supplemental management practices that may be
applied at a disposal site to further enhance contami-
nant immobilization.
These factors must be considered because the physical
and chemical properties of a dredged material, and a
change in those properties, can have a substantial effect
on releaseof contaminants. Understanding these changes
and the interaction between sediments and contaminants
enables selection and management of remediation alter-
natives to minimize contaminant release.2
1.2 Properties of Sediments Affecting
Contaminants
Sediments requiring remediation can vary widely in terms
of physical and chemical properties.3'4 The primary physi-
cal characteristic is texture, orthe distribution of sand, silt,
and day sized particles. Generally, sandy sediments
have little attraction for either toxic metals or synthetic
organics (pesticides and industrial organics). Fine tex-
tured sediments such as silt and clay have a much greater
affinity for all classes of contaminants. Fine-textured
material at the sediment-water interface and suspended
silt and clay particles effectively scavenge contaminants
from the water column. These particles tend to accumu-
late in more quiescent reaches of waterways. Separation
of the less contaminated sandy fraction from contami-
nated sediments can often yield a material clean enough
for disposal without restriction while also reducing the
volume of the contaminated sediment requiring treat-
ment.
Another very important physical property is the organic
matter content. Fine textured sediments, more so than
sandy sediments, generally contain from one to several
percent naturally occurring humic material derived from
the microbial transformation of plant and animal detritus.
Humic material may be present as discrete particulates or
as coatings on clay particles and is important in two
respects: the humic material greatly increases the affinity
of sediments for metals and nonpoiar organic contami-
nants and it serves as an energy source for sediment
microbial populations.
Measurement of in situ water content is a third physical
property of sediments usually important to remediation
decisions.
Sediment acidity and oxidation/reduction status are two
very important chemical parameters.5-6 Strongly acidic
(low pH) conditions can slow microbial activity and in-
crease the soluble levels of toxic metals. Weakly acidic,
neutral, and slightly alkaline conditions (higher pH) favor
metal immobilization processes. The oxidation-reduction
status of a sediment, measured as redox potential, has a
major effect on the retention or release of a number of
metals, either directly or as a result of the difference in
reactions of metals with oxidized and reduced sediment
constituents. Changes in pH and redox potential of
contaminated sediments from their initial condition at a
dredging site to different conditions at a remediation site
can substantially affect contaminant immobilization proc-
esses. Other important chemical properties of sediments
include salinity conditions, sulfide content, the amount
and type of cations and anions, and the amount of
potentially reactive iron and manganese.
1.3 Forms and Reactions of Contaminants
Typical trace and toxic metal contaminants include cop-
per, zinc, cadmium, lead, chromium, nickel, arsenic,
mercury, selenium, and sometimes others. These ele-
ments are usually present in soils and sediments at low
concentrations from natural sources. It is when one or
more of these contaminants is present in elevated con-
centrations that they pose a potential problem. Real
problems exist if these excess metals are released to the
water column or are present in forms readily available to
plants and animals that come in contact with the sediment
material.
Metals dissolved in the water column or pore water are
considered most available to organisms. Metals bound to
clay minerals and humic material by cation exchange
processes are also considered relatively available due to
some equilibrium between these bound metals and dis-
solved metals. On the opposite extreme are metals
bound within the crystal lattice structure of clay minerals.
Metals in this form are essentially permanently immobi-
lized and unavailable. Between these extremes are
potentially available metals. The bulk of metals in con-
taminated sediments are in these potentially available
forms. A listing of some of the common chemical forms of
metals ranging from most available to least available is
presented in Table 1-1.
The chemical properties of sediments also greatly affect
the mobility and biological availability of contaminants.
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Table 1 -1. Availability of Metals in Common
Chemical Forms
A. Readily available:
— dissolved
— exchangeable
B. Potentially available:
— metal carbonates
— metal oxides and hydroxides
— metals adsorbed on, or occluded with, iron oxides
— metals strongly adsorbed, or chelated, with humic
materials
— metals precipitated as su If ides
C. Unavailable:
—metals within the crystalline lattice structure of clay
minerals
Metals may be mobilized or immobilized if the chemical
environment of the sediment or dredged material changes.
Therefore, understanding the influence of the sediment
chemical environment, and controlling changes in this
environment, are important to the selection of disposal
alternativesforcontaminated sediments. Table 1-2 shows
the fate of the potentially available metals as sediment
conditions change.
It should be mentioned that there may be a complemen-
tary interaction between some of these processes as the
pH or oxidation status of a sediment is altered. As metals
are released from one form, they may be immobilized
again by another process. However, the potential effi-
ciency of this complementary interaction of processes
depends on the particular properties of the sediment
material.
Organic contaminants can vary widely in water solubility
depending on their molecular composition and functional
groups. Like metals in a sediment-water system, most
organic contaminants tend to become strongly associ-
ated with the sediment solid phase, particularly the humie
fraction. Thus, at most sites, the distribution of organic
contaminants between dissolved and solid phases is a
function of their water solubility and the percent of
naturally occurring humic materials in the sediment.
However, at heavily contaminated sites, organic contami-
nants also associate with petroleum-based or sewage-
based organics.
Unlike metals, however, organic contaminants do de-
grade. Though all organic contaminants degrade at some
rate, some have half-lives on the order of several dec-
ades. Some organics are subject to enhanced degrada-
tion rates under certain sediment chemical conditions.
Table 1-2. Typical Fate of Potentially Available Metals in a Changing Chemical Environment
Metal Type
carbonates,
oxides, and
hydroxides
adsorbed on iron
oxides
chelated to
humic
sulfides
Initial Condition
salts in the sediment
adsorbed in sediment
chelated in sediment
very insoluble
precipitate
Environmental Change
reductions of pH
sediment becomes
reducing or acidic
Result
release of the metals
as the salts dissolve
iron oxides become
unstable and release
metals
strongly immobilizes metal in both reducing and oxidizing
sediments (However, there is some indication that the
process is less effective if a reduced sediment becomes
oxidized)
sediment becomes
oxidized
sulfides become
unstable, oxidize to
sulfates, and release
the metals
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1.4 References
1. GambreH, R.P., W.H. Patrick, Jr., and R.M. Engler.
A Biogeochemical Evaluation of Disposal Op-
tions. In: Dredging and Dredged Material Dis-
posal, Volume 1, R.L. Montgomery and J.W.
Leach, eds. American Society of Civil Engineers,
1984. pp. 467-477.
2. Gamfarell, R.P., R.A. Khalid, and W.H. Patrick, Jr.
Disposal Alternatives for Contaminated Dredged
Material as a Management Tool to Minimize
Adverse Environmental Effects. DS-78-8, U.S.
Army Engineer Waterways Experiment Station,
Vicksburg, Mississippi, December, 1978.
3. Moore, T.K. and B.W. Newbry. Treatability of
Dredged Material (Laboratory Study). Technical
Report D-76-2, U.S. Army Engineer Waterways
Experiment Station, Vicksburg, Mississippi, 1976.
102pp.
4. Khalid, R.A., R.P. Gambrell, M.G. Vertoo, and
W.H. Patrick, Jr. Transformationsof Heavy Metals
and Plant Nutrients in Dredged Sediments as
Affected by Oxidation-Reduction Potential and
pH. Volume 1: Literature Review. Contract
Report D-77-4, U.S. Army Engineer Waterways
Experiment Station, Vicksburg, Mississippi, 1977.
221 pp.
5. Gambrell, R.P., R.A. Khalid, and W.H. Patrick, Jr.
Chemical Availability of Mercury, Lead, and Zinc
in Mobile Bay Sediment Suspension as Affected
by pH and Oxidation-Reduction Conditions.
Environmental Science and Technology, 14:431 -
436,1980.
6. Khalid, R.A., R.P. Gambrell, and W.H Patrick, Jr.
Chemical Availability of Cadmium in Mississippi
River Sediment. Journal of Environmental Qual-
ity, 10:523-529, 1981.
4
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CHAPTER 2
SEDIMENT TOXICITY ASSESSMENT
2.1 Introduction
Assessing the toxicity of sediments and any potential
threat they pose to human health and the environment is
an important step in the remediation process. Presently,
several different kinds of tools are available to use in
making decisions concerning sediment assessment and
desired levels of remediation. Primary tools include
environmental regulations and sediment assessment
methods; descriptions of their current status form the
major sections of this chapter.
2.2 Environmental Regulations that Relate
to Contaminated Sediments
Section 121(d) of the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA),
as amended by the Superfund Amendments and Reau-
thorization Act of 1986 (SARA), provides that a cleanup
must meet the most stringent standard of all the appli-
cable or relevant and appropriate regulations (ARARs),
whether that standard originates from another federal
environmental law or from a state law. Types of ARARs
include:
1. Chemical-specific ARARs - Health or risk-based
concentration limits or ranges in various environ-
mental media for specif ic hazardous substances,
pollutants, or contaminants. Chemical-specific
ARARs may define protective cleanup levels.
2. Action-specific ARARs - Controls or restrictions
on particular kinds of activities related to man-
agement of hazardous substances, pollutants, or
contaminants. Action-specific ARARs may set
controls or restrictions for particular treatment
and disposal activities.
3. Location-specific ARARs - Restrictions on activi-
ties within specific locations such as flood plains
or wetlands.
Sources of ARARs for the remediation of contaminated
sediments include international agreements and federal
and state statutes and regulations. Major environmental
regulations that may apply to sites with contaminated
sediments are summarized below. EPA has also pub-
lished descriptions of these regulations.1
2.2.1 Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA)
In addition to the provisions for meeting ARARs men-
tioned above, the broader objectives of CERCLA are to
protect human health and the environment by responding
to potential or existing hazardous substance releases,
remediating or cleaning up contaminated areas, and
assessing liability for remediation actions and resource
damages. In general, CERCLA provisions relate eitherto
contamination at abandoned sites where there is a con-
tinuing threat of more widespread contamination or to
emergency spills. Currently used hazardous sites are
generally covered by the Resource Conservation and
Recovery Act (RCRA).
CERCLA provides broad authority to locate areas with
contaminated sediments. EPA can undertake studies or
investigations if it believes a hazardous substance
release has occurred or may occur. Studies on the
degree and extent of contamination and potential routes
of human exposure to a hazardous substance are gener-
ally determined through preliminary assessments and
may include sampling and testing sediments during site
investigations.
2.2.2 Clean Water Act (CWA)
The CWA was designed to restore the physical, chemical,
and biological integrity of the nation's navigable waters.
There are broad, general requirements under the CWA to
locate waters that are not meeting water quality standards
and, by extension, waters that have contaminated sedi-
ments. The CWA also has specific provisions relating to
contaminated sediments: it authorizes the EPA to identify
and remove contaminated sediments in harbors and
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navigable waterways;to identify contaminated sediments
in the Chesapeake Bay; to identify contaminated estuar-
ies in the National Estuary Program (NEP); and to identify
and demonstrate remedial options in the Great Lakes.
This last provision is being fulfilled underthe directions of
the Great Lakes National Program Office (GLNPO) as
part of the Assessment and Remediation of Contami-
nated Sediments (ARCS) program. Finally, the CWA
authorizes the development of criteria which may apply to
dredging and dredged material disposal, assessment,
source control, and remediation.
2.2.3 Resource Conservation and Recovery
Act (RCRA)
RCRA's overall objectives are to minimize the generation
of hazardous waste and to treat, store, and dispose of
hazardous wastes so as to minimize present and future
threats to human health and the environment. Since one
of RCRA's main goals is to prevent the initial release of
hazardous wastes into the environment, all treatment,
storage, or disposal facilities must meet detailed design,
operation, maintenance, and monitoring requirements
before receiving an EPA operating or closure permit.
RCRA permittees, or applicants for RCRA permits.might
have to locate contaminated sediments and RCRA provi-
sions could require a permittee to remediate the sedi-
ments in many circumstances.
2.2.4 Marine Protection, Research, and
Sanctuaries Act (MPRSA)
The major purpose of MPRSA is to regulate the dumping
of all sewage sludge, industrial waste, and dredged
material into the ocean in order to prevent or strictly limit
the dumping into ocean waters of any material that would
adversely affect human health, welfare, or amenities, or
the marine environment, ecological systems, or eco-
nomic potentialities. The U.S. Army Corps of Engineers
(USAGE) and EPA have jointly developed protocols to
determine if dredged materials can be disposed of in the
ocean. These protocols consist of atiered testing scheme
which initially relies on existing information to make a
decision on potential contamination. This may be fol-
lowed by an evaluation of the chemical and physical
characteristics of the dredged material and overall envi-
ronmental conditions at the site. This in turn may be
followed by bioassays and bioaccumulation studies to
determine whether disposal of the material would result in
unacceptable adverse impacts.
2.2.5 Toxic Substances Control Act (TSCA)
TSCA's objective is to ensure that the manufacturing,
processing, distribution, use, and disposal of chemical
substances and mixtures do not present an unreasonable
risk of injury to human health or the environment. TSCA
applies to the procedure for dealing with contaminated
sediments in two ways: first, a contaminant that is
commonly found in sediments in excess of sediment
criteria may be subject to manufacturing bans, and sec-
ond, sediments contaminated with greater than 50 ppm
PCBs may have to be disposed of by TSCA-approved
methods.
2.2.6 Federal Insecticide, Fungicide, and
Rodenticide Act (FIFRA)
FIFRA provisions are similar to TSCA provisions in that
the use of a biocide could be restricted nationwide or in
certain regions of the country if it commonly exceeded
sediment quality criteria. Many of the persistent pesti-
cides have use restrictions under FIFRA and more pesti-
cides may be added to the restricted list.
2.2.7 Clean Air Act (CAA)
The CAA is similar to both FIFRA and RCRA in that
emission control provisions would only become important
if it could be demonstrated that air emissions were re-
sponsible for sediment contamination over wide-spread
areas. Alternatively, air emissions from the treatment and
disposal of contaminated sediments may have to meet
CAA standards.
2.2.8 National Environmental Policy Act (NEPA)
NEPA requires the preparation of an Environmental Impact
Statement (EIS) for many federally-funded projects. EIS
preparation provides an opportunity to explore the options
available for dredging, and disposal of contaminated
dredged material. NEPA's intent is to incorporate envi-
ronmental considerations into decision-making at the
federal level. National dredging projects are typical of the
types of projects that require EISs. NEPA does not
provide the legal authority for making decisions, however,
and all aspects of control of dredging and dredged mate-
rialdisposal are covered by other environmental statutes.
2.2.9 Rivers and Harbors Act (RHA)
The RHA provides authority for the USAGE to carry out
projects for the improvement of navigation. It does not
authorize dredging for environmental improvement (such
as the removal of contaminated sediments). The Water
Resources Development Act of 1990 does provide the
USAGE with some authority to remove contaminated
sediments.
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2.2.10 Endangered Species Act of 1973
Dredge and fill projects, as well as other activities regard-
ing contaminated sediments, can potentially adversely
impact threatened and endangered wildlife species due to
habitat degradation or destruction. Thus, such projects
fall under the jurisdiction of the Endangered Species Act
of 1973.
2.2.11 Great Lakes Water Quality
Agreement (GLWQA)
The GLWQA between Canada and the United States is an
agreement to restore and enhance water quality in the
Great Lakes System. Under the GLWQA, the Interna-
tional Joint Commission Dredging Subcommittee has
developed specific sediment classification protocols to
assist in determining appropriate disposal options for
navigational dredging projects.
2.2.12 State Environmental Statutes that Relate to
Contaminated Sediments
Finally, state laws may also apply to contaminated sedi-
ments. Examples include state requirements for disposal
and transport of radioactive wastes, state approval of
water supply system additions or developments, state
ground-water withdrawal approvals, state water quality
standards, and state air toxics regulations.2
2.3 Current Development of Sediment
Assessment Tools
Although sediments are an extension of the water col-
umn, assessment of sediment toxieity is much more
complex than assessment of water quality. Due to the
nature of sediment chemistry, presence of contaminants
does not necessarily mean that the sediment is toxic. For
example, contaminants may be present but chelated with
humic material in the sediment and thus unavailable.
This problem has become increasingly apparent in recent
years and the EPA is developing a national strategy to
address this issue. Under the lead of the Office of Water,
the following steps are being taken: (1) review of sediment
assessment methods, (2) development of sediment quality
criteria, (3) development of the Toxieity Identification
Evaluation, and (4) discussion of the need for a
consistent, tiered testing approach to sediment quality
assessment.
2.3.1 Sediment Methods Classification
Compendium
In order to meet a growing concern for establishing a
regulatory tool that can be used in the assessment of sites
with suspected sediment contamination, a national sedi-
ment criteria development effortwas undertaken by EPA's
Criteria and Standards Division.3 A Sediment Classifica-
tion Methods Compendium was developed to serve as a
reference for methods that could be used to assess the
quality of chemically contaminated sediments.4 This
compendium describes the various methods, as well as
their advantages, limitations, and existing applications.
These methods are listed and described in Table 2-1.
Each method either directly or indirectly attempts to
delimit levels of contamination within sediments such that
above those levels either (1) acute and/or chronic lexico-
logical effects become manifest or (2) some amount of
bioaccumulation occurs. The sediment quality assess-
ment methods described can be classified into two basic
types: numeric or descriptive (see Table 2-1). Numeric
methods are chemical-specific and can be used to gener-
ate numerical sediment quality values. Descriptive
methods are qualitative and cannot be used alone to
generate numerical sediment quality values for particular
chemicals.
It should be pointed out that the assessment methods in
the compendium are not at equal stages of development,
and that certain methods (or combinations of methods)
are more appropriate for specific management actions
than are others. The compendium does not provide
guidance on which methods to apply for specific situ-
ations or on how different methods can be used as part of
a decision-making framework.4-5
2.3.2 Sediment Quality Criteria (SQC)
Currently, the EPA is working toward the development of
nationally applicable sediment quality criteria, SQC will
represent the EPA's best recommendation of sediment
contaminant concentrations that will not -unacceptably
affect benthic organisms or their uses. SQC will be
developed separately for each contaminant. At current
funding levels, SQC for six non-ionic organic contami-
nants are scheduled to be developed in FY91, with an
additional six to eight criteria documents appearing each
year thereafter.
The equilibrium partitioning (EqP) method is the EPA's
selected method to establish national SQC. The EqP
approach relies on established water quality criteria to
assess sediment toxieity. The first basic assumption of
the EqP approach is that sediment toxieity is correlated to
-------
Table 2-1. Sediment Quality Assessment Methods4
Type
Method
Numeric Descriptive Combination
Concept
Bulk Sediment
Toxicily
Spiked-Sediment
Toxlcity
Interstitial Water
Toxicily
Equilibrium
Partitioning
Tissue Residue
Freshwater Benthic
Community Structure
Marine Benthic
Community Structure
Sediment Quality
Triad
Apparent Effects
Threshold
Test organisms are exposed to sediments that contain
unknown quantities of potentially toxic chemicals. At the
end of a specific time period, the response of the test
organisms is examined in relation to a specified biological
endpoint.
Dose-response relationships are established by expos-
ing test organisms to sediments that have been spiked
with known amounts of chemicals or mixtures of
chemicals.
Toxicity of interstitial water is quantified and identification
evaluation procedures are applied to identify and quan-
tify chemical components responsible for sediment toxic-
ity. The procedures are implemented in three phases: 1)
characterization of interstitial water toxicity, 2) identifica-
tion of the suspected toxicants, and 3) confirmation of
toxicant identification.
A sediment quality value for a given contaminant is deter-
mined by calculating the sediment concentration of the
contaminant that would correspondto an interstitial water
concentration equivalent to the EPA water quality crite-
rion for the contaminant.
Safe sediment concentrations of specific chemicals are
established by determining the sediment chemical con-
centration that will result in acceptable tissue residues.
Methods to derive unacceptable tissue residues are
based on chronic water quality criteria and bioconcentra-
tion factors, chronic dose response experiments or field
correlations, and human health risk levels from the con-
sumption of freshwater fish or seafood.
Environmental degradation is measured by evaluating
alterations in freshwater benthic community structure.
Environmental degradation is measured by evaluating
alterations in marine benthic community structure.
Sediment chemical contamination, sedimenttoxicity, and
benthic infauna community structure are measured on
the same sediment. Correspondence between sediment
chemistry, toxicity, and biological effects is used to deter-
mine sediment concentrations that discriminate condi-
tions of minimal, uncertain, and major biological effects.
An AET is the sediment concentration of a contaminant
above which statistically significant biological effects
(e.g., amphipod mortality in bioassays, depressions in
the abundance of benthic infauna) would always be
expected. AET values are empirically derived from
paired field data for sediment chemistry and a range of
biological effects indicators.
8
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the concentration of the contaminants in the interstitial
water and not to the total sediment concentration. The
second basic assumption is that contaminants partitioned
between the interstitial water and the sediment sorbents
(such as organic carbon) are in equilibrium. Therefore, for
a given contaminant, if the total sediment concentration,
the concentration of sorbent(s), and the partitioning coef-
ficient are known, then the interstitial contaminant con-
centration can be calculated. The interstitial contaminant
concentration can then be compared to established water
quality criteria to assess sediment toxicity.6'7'8
Due to variation in the specific sediment sorbent(s) that
different classes of contaminants sorb to, methodologies
for deriving SQC vary with different classes of com-
pounds. For non-ionic organic chemicals the methodol-
ogy requires normalization to organic carbon. For metal
contaminants a methodology is under development and is
expected to require normalization to acid volatile sulfide.
2.3.3 Toxicity Identification Evaluation (TIE)
Over the past two years, the National Effluent Toxicity
Assessment Center (NETAC) at the Environmental Re-
search Laboratory in Duluth, Minnesota has been devel-
oping and publishing guidance concerning methods to
identify specific causes of acute toxicity in aqueous
samples. These TIE methods, although originally devel-
oped for effluents, have been applied successfully to toxic
aqueous sediment fractions (pore water, elutriates). The
ability to identify compounds responsible for sediment
toxicity could prove to be critical to initiating control of their
release by point source dischargers and also could be
helpful for attributing contamination to specific historical
discharges for the purpose of remedial activities.
NETAC's assistance in this project will target high priority
sediment toxicity problems, preferably in systems with a
limited number of dischargers. In addition to identifying
the source of toxicity problems, NETAC's analysis may
include recommendations on the methods for solving
these problems. These initial cases will also serve as
models for conducting sediment TIEs.
2.3.4 Tiered Testing
The development of a consistent tiered testing methodol-
ogy may provide a uniform basis for EPA decisions
regarding the regulation and remediation of contaminated
sediments. The need for such a methodology is currently
under discussion at EPA. One possible model is the
tiered testing scheme used to evaluate the suitability of
dredged materials for ocean dumping. This scheme is
described in the "Green Book,"currently being updated by
the EPA's Office of Marine and Estuarine Protection
(OMEP) and the USAGE.9 The testing scheme consists
of four tiers:
1. Analysis of existing information and identification
of contaminants of concern.
2. Evaluation of sediment and site conditions.
3. Evaluation of acute bioassays and short-term
bioaccumulation studies.
4. Evaluation of chronic bioassays and long-term
bioaccumulation studies.
Evaluation at successive tiers is based on increasingly
extensive and specific information that may be more time-
consuming and expensive to generate, but that provides
increasingly comprehensive evaluations for environmental
effects.
2.4 References
1. USEPA. Contaminated Sediments: Relevant
Statutes and EPA Program Activities. EPA 506/
6-90/003, U.S. Environmental Protection Agency,
Washington, D.C., 1990.
2. USEPA. National Oil and Hazardous Substance
Pollution Contingency Plan. Final Rule, U.S.
Environmental Protection Agency, February,
1990.
3. Zarba, C. National Perspective on Sediment
Quality. In: Contaminated Marine Sediments -
Assessment and Remediation. National Acad-
emy Press, Washington, D.C., 1989.
4. USEPA. Sediment Classification Methods
Compendium. Final Draft Report, U.S. Environ-
mental Protection Agency, June, 1989.
5. USEPA. Report of the Sediment Criteria Sub-
committee of the Ecological Processes and Ef-
fects Committee: Evaluation of the Sediment
Classification Methods Compendium. EPA-SAB-
EPEC-90-018, U.S. Environmental Protection
Agency, Washington, D.C., 1990.
6. Di Toro, D.M. A Review of the Data Supporting
the Equilibrium Partitioning Approach to Estab-
lishing Sediment Quality Criteria. In: Contami-
nated Marine Sediments - Assessment and
Remediation. National Academy Press, Wash-
ington, D.C., 1989.
9
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USEPA. Briefing Report to the EPA Science
Advisory Board on the Equilibrium Partitioning
Approach to Generating Sediment Quality Crite-
ria. EPA 440/5-89-002, U.S. Environmental Pro-
tection Agency, Washington, D.C., April, 1989.
USEPA. Report of the Sediment Criteria Sub-
committee of The Ecological Processes and Ef-
fects Committee - Evaluation of The Equilibrium
Partitioning (EqP) Approach for Assessing Sedi-
ment Quality. EPA-SAB-EPEC-90-006, U.S.
Environmental Protection Agency, Washington,
D.C., February, 1990.
USEPA and USAGE. Draft Ecological Evalu-
ation of Proposed Discharge of Dredged Material
into Ocean Waters. EPA-503-8-90/002, U.S.
Environmental Protection Agency, Washington,
D.C., January, 1990.
to
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CHAPTERS
PROCEDURES FOR CHARACTERIZATION OF CONTAMINATED SEDIMENTS
3.1 Introduction
Characterization of contaminated sediments begins with
the identification of contaminants present. While a list of
contaminants is important, a description of the vertical
and horizontal distributions of the contaminants within the
sediments is also necessary due to the heterogeneity of
most sediments. Characterization of the sediments is
also important, as sediment characteristics will have
profound effects on contaminant availability (see Chapter
One) and should impact remediation decisions. Sedi-
ment characterization should include physical and chemi-
cal characteristics but also distributions of these within the
site of concern. Modeling sediment transport and con-,
taminant fate and transport will give additional insight into
sediment characteristics. Key to efficient and economical
characterization is the development of a sampling plan
and the selection of the proper sampling method.
3.2 Sampling Plan
In order to properly sample and characterize contami-
nated sediments, extensive planning must first be done.
The sequence in the planning stage should include:
1.
2.
3.
4.
Identification of sampling purposes and
objectives.
Compilation of available data on the site of
concern.
Collection of preliminary field data.
Development of a detailed sampling plan.
Developing a sampling plan appropriate for the site and
sampling objectives increases the quality of the site
characterization and minimizes characterization costs.
Unfortunately, due to site variability, a systemized sam-
pling plan applicable to all sites is not feasible.
3.2.1 Identification of Sampling Purposes and
Objectives
The scope of effort is dependent on this decision. Pur-
poses for sediment sampling and testing might include:
1. Determine distribution of specific contaminants.
2. Determine sediment contaminant mobility.
3. Determine existing impacts on aquatic/benthic
fauna.
4. Determine disposal alternatives (regulatory).
5. Determine disposal alternatives (treatability).
No single sampling/analysis plan will serve all these
purposes equally well.
3.2,2 Compilation of Available Data
This data should include the following:
1.
2.
3.
4.
6.
7.
8.
Water depths/tidal fluctuations.
Obstructions (bridges, pipelines, etc.).
Access sites for mobilizing equipment.
Sediment depths (dredging or construction
history).
Sources of contaminants (point and non-point)
and other factors affecting contaminant
distributions.
Hydraulic/other factors affecting sediment
distribution.
Historic sediment quality data.
Survey benchmarks (for referencing sediment
and water elevations).
3.2.3 Collection of Preliminary Field Data
Given the costs of sampling and of laboratory analyses, it
is prudent to conduct some cursory field studies before
developing the sampling and analysis plan. Such studies
should be mandatory where any existing physical infor-
mation is lacking. The amount of time and money that can
be saved by simply visiting the site in a small boat and
poking a long stick in the mud cannot be overestimated.
11
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3.2.4 Development of a Detailed Sampling Plan
Once the lirst three steps have been completed, the
specifics of the sampling and analysis plan can be devel-
oped. These include contractual, logistical, and statistical
considerations. The plan developed as a part of step four
should include details on: ;
1. Locations of samples (lateral and vertical). .
2. Types of samples (grab or core).
3. Number and volumes of samples required.
4. Sampling procedures and equipment.
5. Supporting vessels/equipment.
6. Types of analytical tests required.
7. Quality Assurance Program Plan (QAPP) for
sampling and analysis.
8. Cost estimate.
3.3 Sampling Methods
There are a number of sampling devices that are pres-
ently being used to collect samples. Choosing the most
appropriate sediment samplerforthe study will depend on
fhe requirements of the sampling plan. Attention should
be paid to sample linings: metal linings may introduce
metal contaminants into the sediment samples; plastic
linings may introduce organic contaminants into the
sediment samples.
Biological collections are generally accomplished by trawl-
ing or dredging. Sediment collections have been made
with spoons, scoops, trowels, core samplers, and grab
samplers.
3.3.1 Spoons, Scoops, and Trowels
Spoons, scoops, and trowels are only useful in shallow
water. They are less costly than other samplers, easy to
use, and may be useful if numerous samples are in-
tended; their low cost allows disposal between sample
sites. In general, however, these devices are somewhat
undesirable because the reproducibility of sampling area,
depth, and volume from one sampling site to another is
poor. They also tend to disrupt the sediment during
sampling.1
3.3.2 Core Samplers
These may be used in both shallow and deep aquatic
systems on a variety of substrate conditions. Core
samplers are generally preferred over other samplers
because (1) core samplers can sample to greater depth,
(2) core samplers maintain the complex integrity of the
sediment, and (3) core samplers do not disturb the sub-
strate as much as other sampling procedures.2
Core samplers have several limitations: (1) core samplers
do not work well in sandy or rocky substrates, (2) core
samplers collect smaller amounts of sediment and
therefore may require additional sampling, and (3) most
coring devices are expensive, difficult to handle, and,
consequently, have limited use under moderate wave
conditions.
There are many different types of core sampling equip-
ment that may be used for sediments. Some require the
use of a tripod or truck mounted drill rig operated on a
floating plant (barge). Some hand held units can be
operated from smaller vessels. Core sampling devices
include the split-spoon, the piston-tube or Chicago tube,
the vibracore, and hand augers.
The split-spoon sampler is driven by a hammer or weight
into the sediment. This method is especially suited for
compacted sediments. Good recovery of samples in
loose sediments is less dependable. The spoon is typi-
cally 2-3 inches in diameter and 2-5 feet long. Successive
vertical samples can be taken by driving casing (5 inch
pipe) and cleaning out the drill hole between samples.
The piston-tube or Chicago tube sampler is well suited for
soft, fine-grained sediments. The sampler is advanced to
the starting depth and a tube (typically 3-4 inch diameter)
extended hydrauiically. Recovery is usually very good
since the sample is held in the tube by a partial vacuum.
Discrete vertical samples can be obtained without casing.
The vibracore is a long continuous tube that is driven into
the sediment using a vibrating action. This method is
suited to soft, noncompacted sediments. The entire core
is withdrawn and the tube cut into segments for sample
extraction. Good recovery with this method requires that
the tube penetrate a layer of compacted material, which
forms a "cap" at the bottom. The vibration of the tube has
been known to consolidate the sample and lose some
vertical integrity (a 5-foot drive might produce a 4-foot
sample).
Hand augers can be used for sampling very shallow areas
or on river banks. Hand operated corers, deployed by a
cable from a boat, have been used to collect shallow
cores.
3.3.3 Grab Samplers
Grab samplers are less expensive, easier to handle, and
often require less manpower than core samplers. Unfor-
tunately, grab samplers cause considerable disruption of
12
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the sediment. Dredge samplers promote loss of the fine-
grained fraction of the sediment as well as water soluble
compounds and volatile organic compounds (VOCs) which
may be present in the sediment. One important criterion
for selection of the proper grab sampler is that it consis-
tently collect samples to the required depth below the
sediment.
Grab samplers, such as the Ponar and Eckman dredge
samplers, are small, lightweight, and can be operated by
hand from a small boat. They only collect surface sedi-
ments (top 3-6 inches). They have problems with any
consolidated (hard packed) deposits. For larger volumes
of sample, sometimes needed for treatability tests, a
small, commercial clamshell dredge (1 -3 cubicyard bucket)
can be used.
3.3.4 Other Sampling Considerations
In conjunction with sediment toxicologic assessments,
the type and degree of contamination in the interstitial
water should be determined. Immediate collection of the
interstitial water is recommended since chemical changes
may occur even when sediments are stored for a short
period of time. Collection of the sediment interstitial water
can be accomplished by several methods: centrifugation
with filtration, squeezing, suction, and equilibrium dialy-
sis. Each method may alter the original water chemistry.
Therefore, decisions about methods forcollecting Intersti-
tial water should be based on expected contaminants.
Sediment samples should be separated from the collec-
tion devices and transported in plastic, polyethylene, or
glass containers. Samples that contain volatile com-
pounds should be refrigerated (4° C) or kept on ice to
prevent further volatilization. Sediments that are sus-
pected of organic contamination should be transported in
brown, borosilicate glass containers with teflon lid liners.
Plastic or polycarbonate containers are recommended for
metal-bearing sediments. Additional information on
sample containers, preservation, storage times, and vol-
ume requirements are available in other guidance docu-
ments.3
3.4 Physical and Chemical Analyses
The type of analysis performed on sediment collected is
specific to the purpose and objectives of the plan. There
is no "standard" laundry list of analyses which is
appropriate to all cases. Some important analyses for
consideration are identified in the following paragraphs.
Francingues et al4 provide guidance on testing sediment
characteristics.
Physical characteristics often measured are particle size
and distribution, organic carbon or volatile mattercontent,
and total solids/specific gravity. Particle size is usefully
described by the general size classes of gravel, sand, silt,
and clay. Organic carbon should be measured by high
temperature combustion rather than chemical oxidation.
The latter method does not necessarily fully degrade all
carbon classes. Total solids/specific gravity analyses
both require a dry sample and are performed in conjunc-
tion with each other.3
Important chemical analyses include those for pH, oxida-
tion-reduction, salinity conditions, and sulfide content as
well asthe amount and type of cations and anions, andthe
amount of potentially reactive iron and manganese. Much
can be inferred from the pH and oxidation-reduction
conditions when they are analyzed in conjunction with the
physical properties.5 The pH becomes a problem when
the dredged material has a pH below 5 or above 8.5 or
when it changes during handling and disposal. Whether
the sediments are oxidizing or reducing will affect the
availability of various contaminants during handling and
disposal of the sediments.6
3.5 Modeling Sediment Transport and
Contaminant Fate and Transport
Sediment transport and contaminant transport and fate
models have two applications: (1) they can be used as a
screening tool in predicting the environmental and health
impactsfrom contaminant exposure during various reme-
diation actions and (2) they can be used diagnostically to
investigate sources of contamination. Current models are
limited in their predictive ability to function as a screening
toolorcrude design model, but are developed to such a
degree that they are being applied in this respect for the
Buffalo River, New York. Diagnostic modeling is being
dbneforthe Sheboygan River, Wisconsin.
Sediment transport models are linked to hydrodynamic
models and predict sediment movement due to circula-
tion. Different models have been developed for a variety
of sediment environments including lakes, harbors, estu-
aries, coastal areas, and rivers. The models may be
one-, two-, orthree-dimensional, depending on the nature
of the water body. The one-dimensional models,
HYDRO1D-DYNHYD, HYDRO1D-RIVMOD, and HSPF,
are used for rivers, streams, and watersheds. The two-
dimensional model, HYDRO2D-V, is generally the first
choice of the Environmental Research Laboratory (ERL)
and has application for estuaries, shallow lakes and bays,
and streams. The HYDRO2D-V is being used to model
arsenic contamination in New Jersey and is planned for
use in Montana mining district streams and in modeling
the south bay in San Francisco Bay. The three-dimen-
13
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sfonal model, HYDRO3D-V, has application for stratified
bodies of water, such as lakes, and has been tested in
PCS studies for Green Bay, Wisconsin. Correct data is
important to proper functioning of these models. These
models are in different stages of refinement, but all are
available from the ERL in Athens, Georgia.7'8-9
Fate and transport models mimic the physical and chemi-
cal environment of sediments and predict how contami-
nants and sediments interact, particularly as conditions
change. The HYDRO2D-V, also used as a sediment
transport model, has been used to model adsorbed con-
taminants, but does not incorporate other contaminant
processes. The WASP4 model is a general purpose,
mass balance model incorporating a number of parame-
ters and is considered the state-of-the-art fate and trans-
port model by ERL and a number of EPA offices. The
WASP4 has been adopted fortoxics management by the
Great Lakes National Program Office. Studies using
WASP4focus on Green Bay, Lake Ontario, and Saginaw
Bay. The WASP4 also simulates fish and food chain
btoaccumulation and is being used to model these in the
Buffalo River, New York; the Sheboygan River, Wiscon-
sin; and Saginaw Bay, Michigan.
3.6 References
1. USFWS. U.S. Fish and Wildlife Service Lands
Contaminant Monitoring Operations Manual:
Sediment Sampling Reference Field Methods,
Appendix I. Final Report, U.S. Fish and Wildlife
Service, 1989.
2. USEPA. Report of the Sediment Criteria Sub-
committee of the Ecological Processes and Ef-
fects Committee: Evaluation of the Sediment
Classification Methods Compendium. EPA-SAB-
EPEC-90-018, U.S. Environmental Protection
Agency, Washington, D.C., 1990. 25 pp.
3. USEPA and USACE. Draft Ecological Evalu-
ation of Proposed Discharge of Dredged Material
into Ocean Waters. EPA-503/8-90-002, U.S.
Environmental Protection Agency, Washington,
D.C., 1990.
4. Francingues, N.R., M.R. Palermo, C.R. Lee, and
R.K. Peddicord. Management Strategy for Dis-
posal of Dredged Material: Contaminant Testing
and Controls. Miscellaneous Paper D-85-1,
USACE Waterways Experiment Station,
Vfcksburg, Mississippi, 1985.
5. USACE. Dredging and Dredged Material Dis-
posal. EM 1110-2-5025, U.S. Army Corps of
Engineers, Washington, D.C., 1983.
6. Gambrell, R.P., R.A. Khalid, and W.H. Patrick, Jr.
Disposal Alternatives for Contaminated Dredged
Materials as a Management Tool to Minimize
Adverse Environmental Effects. DS-78-8, U. S.
Army Corps of Engineers, Washington, D.C.,
1978.
7. Hayter, E.J. and S.C. McCutcheon. Finite Ele-
ment Hydrodynamic and Cohesive Sediment
Transport Modeling System FCSTM-H. U.S.
Environmental Protection Agency, Environmental
Research Laboratory, Athens, Georgia, 1988.
8. Sheng, Y.P., M. Zakikhani, and S.C. McCutcheon.
Three Dimensional Hydrodynamic Model for
Stratified Flows in Lakes and Estuaries
(HYDRO3D): Theory, User Guidance, and
Applications for Superfund and Ecological Risk
Assessments. EPA/600/"*/***, U.S. Environ-
mental Protection Agency, Environmental Re-
search Laboratory, Athens, Georgia, 1991.
9. Sheng, Y.P., P.E. Eliason, X. J. Chen, and J.K.
Choi. A Three-Dimensional Numerical Model of
Hydrodynamics and Sediment Transport in Lakes
and Estuaries: Theory, Model Development, and
14
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CHAPTER 4
REMOVAL AND TRANSPORT
4.1 Introduction
The process of selecting removal and transport technolo-
gies should be driven by treatment and/or disposal deci-
sions. This is because treatment/disposal options typi-
cally have the higher costs and are more controversial
from a social, political, or regulatory perspective. For
example, incineration would require less energy if the
waste to be incinerated had a higher solid content. If it is
the treatment of choice for a particular site, then dredges
which produce a low solid content slurry (high water
content slurry) may not be a feasible alternative. Other
criteria are also important and will be identified in this
chapter.
Another concern during the removal and transport of
contaminated sediments is the danger of introducing
contaminants into previously uncontaminated areas.
Contamination during these steps occurs primarily from
the resuspension of sediments during removal and from
spills and leaks during transport. Accordingly, the deci-
sion to remove must be made only aftercareful considera-
tion of all non-dredging remedial options, including no
action and in situ containment or remediation. Of course,
the nature of the contamination, or site considerations,
may make removal and transport necessary.
4.2 Removal
To increase efficiency and reduce sediment resuspen-
sion, dredges, operational controls, and barriers should
be used together. Of these, dredges actually remove the
sediments; operational controls and barriers minimize the
resuspension and spread of contaminated sediments
during removal.1 these three removal components are
described below; following are descriptions of possible
small site solutions.
4.2.1 Dredges
In the selection of a dredge type for the removal of
contaminated sediments, four factors should be
considered:2
1. Volume - the volume of material to be removed
will determine the scale of operations and the
time frame available for removal.
2. Location - obstacles (bridges, shallow water,
etc.), distance to the disposal area, and human
use patterns at and near the site are examples of
location concerns.
3. Material -consolidated sediments, large amounts
of debris, and the contaminants of concern im-
pact dredge selection.
4. Pre-treatment - requirements of the sediment
treatment technology (dewatering, etc.) must also
be considered.
There are three types of dredges available forthe removal
of contaminated sediments: mechanical, hydraulic, and
pneumatic. Historically, mechanical and hydraulicdredges
have been the most commonly used in the United States
(they are compared in Table 4-1). Pneumatic dredges are
relative newcomers and are generally foreign made; they
have been developed specifically for contaminated sedi-
ments. All three dredge types are described in more detail
below. In addition to the references cited in this chapter,
the following documents will also assist in the selection of
the proper dredge for the site: USAGE,3 Hayes,4-5 and
McClellan et al.6
Mechanical dredges remove sediments by the direct
application of mechanical force to dislodge sediment
material. The force is commonly applied, and the material
scooped away, with a bucket. The most commonly used
mechanical dredge is the clamshell dredge. The clam-
shell dredge has widespread application forthe removal
of contaminated sediments, although the use of a modi-
fied, watertight bucket may be required. Conventional
earth-moving equipment (backhoes, etc.) may also be
considered for sediment removal in certain scenarios.
Dipper dredges, bucket ladder dredges, and dragline
dredges should not be used in the removal of contami-
nated sediments due to excessive sediment resuspen-
sion.2 Clamshell dredges and earth-moving equipment
are summarized in Table 4-2. Relative cost is applicable
across Tables 4-2,4-3, and 4-4.
15
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Table 4-1. Comparison of Hydraulic and Mechanical Dredges2
Dredge Type
Advantages
Disadvantages
Mechanical:
excavation can proceed at the sediment's in
situ water content
dredges are highly maneuverable
no depth limitations for clamshell dredges
all types of debris can be removed
good dredging accuracy
potential for large amounts of sediment
resuspension
dredged material must be rehandled
production capacity is generally lower than Hydraulic
unit costs are typically higher than Hydraulic
Hydraulic:
resuspension of sediment is limited
dredged material can be piped directly to the
disposal area, eliminating the need for
rehandling
production capacity is generally higher than
Mechanical
unit costs are typically lower than Mechanical
large volume of water-removed with the sediment
must be treated prior to disposal or release
slurry pipelines can obstruct navigational traffic
most debris cannot be removed hydraulically
nonhopper dredges cannot be operated in rough water
Table 4-2. Comparison of Selected Mechanical Dredges7
Technique
Clamshell
Conventional
Excavation
Equipment
Applications
Small volumes of sediments;
confined areas and near
structures; removal of bottom
debris; nonconsolidated
sediments; interior water-
ways, harbors
Small volumes of sediments in
shallow or dewatered areas
Limitations
Low production
rates; cannot
excavate highly
consolidated
sediments or
solid rock
Restricted
capacities and
reach; limited to
very shallow
water depths
Secondary
Impacts
Considerable
resuspension
of sediments
Considerable
resuspension
of sediments
Availability/
Transportability
Dredge head can
be moved over
existing roads as-is
and mounted on
conventional crane;
widely available
Can be moved
over existing
roads; widely
available
Production
(yd3/hr)
30-600
60-700
Maximum
Depth of
Use (feet)
100
N/A
Relative
Cost
Low
Low
Hydraulic dredges use centrifugal pumps to remove
sediments in a liquid slurry form. They are widely avail-
able in the U.S. Often a cutterhead, or similar device, is
lilted to the suction end of the dredge to assist in dislodg-
ing bottom materials. New dredge designs attempt to
reduce the amount of resuspension caused by dredging
and to decrease the water content of the pumped slurry.
Common hydraulic dredges are compared in Table 4-3.
pneumatfcdredgesareasubcategoryofhydraulicdredp.es
that use compressed air and/or hydrostatic pressure
instead of centrifugal force to remove sediments. Thus,
they produce slurries of higher solid concentrations than
hydraulic dredges. They also cause less resuspension of
bottom materials. Common pneumatic dredges include
Airlift dredges, the "Pneuma," and the "Oozer" (both of
Japanese design). Although pneumatic dredges have
been used extensively in Europe and Japan, they have
only limited availability in the United States.7'8 Pneumatic
dredges also require a minimum of 71/2 feet of water—
deeper than for mechanical or hydraulic dredges—to
function properly. Table 4-4 compares common pneu-
matic dredges.
4.2.2 Operational Controls
Operational controls, like proper dredge selection, assist
in reducing resuspension of sediments. These controls
include the cutter speed, the depth of cut, the swing speed
and/or speed of advance, and the positioning of equip-
ment. Operator experience is of primary importance in
implementing operational controls.
One example of operational control is cut technique.
Because sediments are often unstable, disruption of a
side slope may cause significant resuspension of con-
1.6
-------
taminated sediments. One solution to the problem of
resuspension is dredging technique. Typically, when
dredging a side slope, a box cut is made and the upper half
of the cut sloughs to the specified slope. To minimize
resuspension, the specified slope should be cut by mak-
ing a series'of smaller boxes. This method, called
"stepping the slope," will reduce but not eliminate slough-
ing.9 If stepping the slope causes unacceptable resus-
pension, it may be best to avoid dredging completely (if
risk assessment shows this to be a viable alternative).
Capping sediments in situ may successfully reduce con-
taminant mobility.
4.2.3 Barriers
Barriers help reduce the environmental impact of sedi-
ment removal. Structural barriers include dikes, sheet
pilings, caissons, and other weir enclosures. Non-struc-
tural barriers include oil booms, pneumatic barriers,
sediment traps, silt curtains, and silt screens. Application
of barrier options is site specific and functions to control
contaminants only during removal.
4.2.4 Small Site Solutions
Several different solutions may be viable for removing
contaminated sediments from a small site. For example,
many small sites may be found in shallow lagoons,
marshes, or streams, which do not permit the operation of
deep-draft, barge-mounted dredges. Horizontal auger-
cutter dredges have adraft of less than two feet and may
be able to operate under such conditions. They are also
typified by low resuspension of sediment, making them
viable alternatives for the removal of contaminated sedi-
ments. The Mud Cat is a common type of horizontal
auger-cutter dredge.10
It also may be possible to use divers with hand-held
dredges to clean up particular types of contaminated
sites.7 For example, Environment Canada oversaw the
clean-up of a perchloroethylene and carbon tetrachloride
spill in the St. Clair River. These chemicals formed visible
bubbles on the sediment that divers could identify and
remove with specially designed hand-held dredges. By
doing this, the contaminants were collected in a relatively
Table 4-3. Comparison of Selected Hydraulic Dredges7
Technique
Portable
Hydraulic
(including
small
cutterhead)
Hand-held
Hydraulic
Plain
Suction
Cutterhead
Applications
Moderate volumes
of sediments; Takes
and inland rivers;
very shallow depths
(to 18 inches)
Small volumes of
solids or liquids in
calm waters; for
precision dragging
Large volumes of
free-flowing
sediments and
liquids; shallow
waters and interior
waterways
it
Large volumes of
solids and liquids;
up to very hard and •
cohesive sediments;
calm waters
Limitations
Limited to waves of
less than one foot;
depending on
model, has low
production rates
and limited depth
Operated from
above-water units
only in shallow
waters
Dredged material
80-90% water;
cannot operate in
rough, open waters;
susceptible to
debris damage; can
cause water traffic
disruption
Dredged material is
80-90% water;
cannot operate in
rough, open waters;
susceptible to
damage and weed
clogging
Secondary
Impacts
Moderate
resuspension
of sediments
: Moderate
resuspension
of sediments
Moderate
resuspension
of sediments
Moderate
resuspension
of sediments
Availability/
Transportability
Readily moved
over existing
roads, may
require some
disassembling;
widely available
Easily moved
over existing
roads; can be
assembled using
commonly
available
equipment
Transport in
navigable waters
only
Transport in
navigable waters
only; wide
availability
Vessel
Length/
Draft
(feet)
25-50/
2-5
N/A
100/5-6
50-250/
3-14
Production
(yd3/hr)
50-1850
10-250
25-
10,000
25-
10,000
Maximum
Depth of
Use (feet)
50
1000
60
50
Relative
Cost*
Low
Low
Med.
Med.
•4-Costs vary with site characteristics; cutterhead dredges may be the cheapest hydraulic dredge for a project involving more than a few
thousand cubic yards.
17
-------
Table 4-4. Comparison of Selected Pneumatic Dredges7
Technique
Airlift
Pnouma
Oozor
Applications
Deep dredging of
loose sediment
and liquids; for
use in interior
waters
Nonconsolidated
solids and liquids
in interior
waterways
Soft sediments
and liquids from
river beds or
harbor bottoms;
relatively shallow
depths
Limitations
Not for consolidated
sediments; dredged
material is 75%
water
Not for consolidated
sediments; not for
shallow waters; may
cause obstruction
to water traffic
Modest production
rates; may.cause
obstruction to water
traffic
Secondary
Impacts
Resuspension
of sediment is
low
Resuspension
of sediment is
low
Resuspension
of sediment is
low
Availability/
Transportability
Dredge head can
be moved over
existing roads; not
widely available in
the United States
Dredge head can
be moved over
existing roads;
not widely
available in the
United States
Dredge head can
be moved over
existing roads; not
widely available in
the United States
Vessel
Length/
Draft
(feet)
100/3-6
100/5-6
120/7
Production
(yd3/hr)
60-390
60-390
500-800
Maximum
Depth of
Use (feet)
N/A
150
N/A
Relative
Cost
Med.
High
High
concentrated form, thereby avoiding the need to remove
and treat large amounts of sediments. This technique
was particularly appropriate since dredges available at
the time of the spill (1985) would have caused consider-
able resuspension of the contaminants.11 If divers are
used in removing contaminated sediments, suits that
prevent skin contact with the water and that are impervi-
ous to contaminant penetration may be required. Emer-
gency medical back-up units may also be important. Risk
to humans may be avoided by using Remote Operated
Vehicles (ROVs) in place of divers. ROVs may be as
effective as divers in many situations where divers might
be considered.
Small sites may also be accessible to isolation and
subsequent excavation. For example, if the contami-
nated sediments are found in a small stream, the flow
could be blocked and diverted with cofferdams and the
sediments subsequently removed with a backhoe.7
4.3 Transport
The primary emphasis during transport is towards spill
and leak prevention. Transport options include pipelines,
barges or scows, railroads, trucks, or hopper dredges.
Selection of transport options will be affected by both
dredge selection and pre-treatment and treatment deci-
sions.
During transport, spills occur primarily during the loading
and unloading of sediments and special care should be
takenduringthese operations. The impactofspiltsduring
transport may further be minimized by careful equipment
and route selection. Finally, all options used in the
transportation of contaminated wastes should be decon-
taminated after use. Operational controls for transport
options are listed in Table 4-5.
4.4 Compatibility With Downstream
Processing
Two additional factors to consider when making dredging
removal and transport decisions are distance to the
disposal site and compatibility with disposal processes.
Mechanically dredged sediments are usually transported
by barge and/or truck; hydraulically dredged sediments
are usually piped directly to the processing site. Because
of the mass and volume of water in the slurry, transporting
dredged material by tank truck or rail is prohibitively
expensive. Therefore, hydraulic dredging may not be
feasible if the processing site is not nearby. Furthermore,
depending on the processing technology, slurried sedi-
ments may have to be dewatered prior to treatment, thus
adding to cost.
4.5 References
1. Averett, D.E., B.D. Perry, and E.J. Torrey. Re-
view of Removal, Containment, and Treatment
Technologies for Remediation of Contaminated
Sediments in the Great Lakes. Miscellaneous
Paper EL90-25, U.S. Army Corps of Engineers,
Vicksburg, Mississippi, 1990.
18
-------
Table 4-5. Controls for Transport Options1
Pipeline
Controls
Pipeline
Routing
Pipeline
Selection
Leak
Detection
Redundancy of
Safety Devices
Barge/Scow
Controls
Loading/
Unloading
Pump
Controls
Route/
Navigation
Decontamination
Rail
Controls
Route
Selection
Car
Selection
Loading/
Unloading
Decontamination
Truck
Controls
Route
Selection
Truck
Selection
Loading/
Unloading
Decontamination
Hopper Dredge
Controls
Loading/
Unloading
Pump
Controls
Route/
Navigation
Decontamination
2. Sukol, R.B. and G.D. McNelly. Workshop on 8.
Innovative Technologies for the Treatment of
Contaminated Sediments, June 13-14, 1990.
EPA/600/2-90/054, U.S. Environmental Protec-
tion Agency, Cincinnati, Ohio, 1990.
3. USAGE. Dredging and Dredged Materials Dis- 9.
posal. EM 1110-2-5025, U.S. Army Corps of
Engineers, Washington, D.C., 1983.
4. Hayes, D.F. Guide to Selecting a Dredge for
Minimizing Resuspension of Sediments. Envi- 10.
ronmental Effects of Dredging, Technical Notes.
No. EEDP-09-1, U.S. Army Engineer Waterways
Experiment Station, Vicksburg, Mississippi, 1986.
5. Hayes, D.F. Sediment Resuspension by Selected
Dredges. Environmental Effects of Dredging, 11.
Technical Notes. No. EEDP-09-2, U.S. Army
Engineer Waterways Experiment Station,
Vicksburg, Mississippi, 1988.
6. McLellan, T.N., R.N. Havis, D.F. Hayes, and G.L.
Raymond. Field Studies of Sediment Resuspen-
sion Characteristics of Selected Dredges. Tech-
nical Report No. HL-89-9, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, Mis-
sissippi, 1989.
7. USEPA. Responding to Discharges of Sinking
Hazardous Substances. EPA540/2-87-001, U.S.
Environmental Protection Agency, Cincinnati,
Ohio, 1987.
Herbich, J.B. Developments in Equipment De-
signed for Handling Contaminated Sediments.
In: Contaminated Marine Sediments - Assess-
ment and Remediation. National Academy Press,
Washington, D.C., 1989.
USAGE." Disposal Alternatives for PCB-Gon-
taminated Sediments from Indiana Harbor, Indi-
ana, 2 Vols. Final Draft, U.S. Army Corps of
Engineers, Vicksburg, Mississippi, 1987.
Ebasco Services Incorporated. Final Supple-
mental Feasibility Study Report: Marathon Bat-
tery Company Site (Constitution Marsh and East
Foundry Cove) Village of Cold Springs, Putnam
County, NY, Ebasco Services Incorporated, 1986.
Rogers, G.K. The St. Clair Pollution Issue. Water
Research Journal of Canada, 21(3): 283-294,
1986.
-------
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CHAPTERS
PRE-TREATMENT
5.1 Introduction
Pre-treatment technologies are defined as those meth-
ods that prepare dredged materials for additional treat-
ment and/or disposal activities.1 They are not effective in
the removal or treatment of toxic materials in sediments.
Pre-treatment decisions are greatly influenced by dredg-
ing, treatment, and disposal decisions. Pre-treatment
objectives include:
1. To enhance or accelerate settling of the dredged
material solids.
2. To reduce the water content of the dredged
material solids.
3. To separate coarser, potentially cleaner solids
from the fine-grained, more contaminated solids
(particle classification).
4. To reduce the overall cost of the remedial action.
Pre-treatment technology types include slurry injection,
dewatering, and particle classification. They are primarily
applicable to hydraulically dredged sediment.1 Handling
and rehandling concerns should also be addressed in
pre-treatment decisions concerning contaminated sedi-
ments.
Pre-treatment literature uses a number of definitions in
referring to the solid/water ratio in sediments and slurries.
Percent solid (or solid content) is defined as the ratio of
solid mass to total sediment mass. In this document,
percent wafer (or water content) and percent moisture (or
moisture content) are equivalent; both are defined as the
ratio of water mass to total sediment mass. (Water
content also has a geotechnical engineering definition in
which water content is defined as the ratio of water mass
to solid mass.2) As long as water is the only liquid in the
sediment percent solid and percent water (or percent
moisture) are equivalent to each other. For example, 30
percent solid is equivalentto 70 percent water. Obviously,
contaminants may be found in both the solid and water
fractions and add weight to both fractions, but this added
weight will not be addressed in this document. Finally, the
literature generally (although not always) speaks of per-
cent water when discussing the slurries generated by
dredging and when discussing disposal options. On the
other hand, the literature speaks of percent solid when
discussing pre-treatment products and treatment require-
ments. This protocol will be followed in this handbook.
5.2 Slurry Injection
Slurry injection is the injection of chemicals, nutrients, or
microorganisms into the dredged slurry. Slurry injection
is described first in order to emphasize the mixing advan-
tage that accrues if the injection occurs as the sediment
is dredged, prior to passage through the transport pipe-
line. As mechanically dredged sediments are not piped,
this mixing advantage appliesonly to hydraulically dredged
sediments.
Chemical injections condition the sediment for further
treatment and/or accelerate the settling of suspended
solids. Promotion of settling may be important because
the small colloidal-sized particles that settle very slowly
are often more highly contaminated than the bulkier
sediments. Chemical clarification is a type of chemical
injection process that increases the settling rate by the
addition of chemical coagulants which promote coagula-
tion or flocculation and hence settling. Coagulants in-
clude inorganic chemicals, such as the salts of iron and
aluminum, and organic polymers. When using chemical
clarification, a settling period must follow the mixing of
coagulant and sediment in orderto complete the process.
Nutrient and/or microbe injections may enhance biode-
gradation of organics, either by providing a suitable envi-
ronment for microbe growth or by supplying the microbes
themselves. Possible nutrient additions include nitrogen,
phosphorus, organic carbon sources, oxygen, and micro-
nutrients, depending on the deficiencies of the sediment.
Microorganisms, cultured to degrade a toxic material, can
be injected into slurries containing that toxin. At present,
microbe injections have not been demonstrated for large
quantities of dredged material.1
21
-------
microbe injections have not been demonstrated for large
quantities of dredged material.1
5.3 Dewatering
The objective of dewatering is to increase the solid
content (decreasethe watercontent) of sediments forone
or more of the following reasons:
1. Dewatered sediments are more easily handled.
2. Dewatering is normally required prior to incinera-
tion to reduce fuel requirements.
3. Dewatering reduces the costs of many treatment
processes, particularly thermal processes.
4. Dewatering is required prior to land disposal.
5. Dewatering reduces the costs of transporting
sediments to their ultimate disposal by reducing
their volume and weight.
In most cases, the percent solids content of a dewatered
sediment is set by the requirements for subsequent
treatment and disposal. Each treatment technology has
an optimum range of percent solid, above or below which
the technology will not operate efficiently and economi-
cally, if at all. For example, combustion requires that the
solid content be greaterthan 24 percent, preferably in the
28-30 percent range for more economical operation.3
Sediments will vary in percent solid depending on location
and dredging technology. Mechanical and pneumatic
dredges remove sediment at or near in situ solid concen-
trations, while hydraulic dredges remove sediments in a
liquid slurry (usually 5-15 percent solid) and are more
likely to require dewatering. Variations in clay and organic
matter content can influence the percent solid achieved
by the various dewatering technologies.
Dewatering technologies can be subdivided into two
general processes: air drying processes and mechanical
processes.
5.3.1 Air Drying Process
"Air drying" refers to those dewatering techniques by
which the moisture is removed by natural evaporation and
gravity or by induced drainage. Airdryingis less complex,
easier to operate, and requires less operational energy
than mechanical dewatering. Air drying also can produce
a dryer sediment than mechanical dewatering, up to 40
percent solids under normal operation and over 60 per-
cent solids with additional drying time or with the use of
underdrainage systems. Air drying processes do, how-
ever, require a larger land area and are more labor
intensive than mechanical processes. Contaminant re-
leases via seepage, drainage, and volatilization during
the dewatering process must also be considered.3
The most widely applicable and economical air drying
process available for sediments is an appropriately
managed confined disposal facility (CDF). CDFs are
engineered structures designed to retain solids during
dredging and provide storage time for gravity drainage,
consolidation, and evaporation. The rate of dewatering
may be accelerated by using underdrains, pumps, or wick
drains. The use of CDFs for dredged material disposal is
discussed in Chapter Seven.
5.3.2 Mechanical Processes
Mechanical dewatering involves processes in which water
is forced out of the sediment through mechanically in-
duced pressures. Mechanical dewatering processes
includethefollowing:filtration, including beltfilterpresses,
chamber filtration, and vacuum rotary filtration; centri-
fuges, including solid bowl and basket; and gravity thick-
ening. Following is a description of these technologies.
Applications, limitations, and relative costs of selected
dewatering technologies, including CDFs, are identified
in Table 5-1.
Belt filter presses dewater by carrying the sediment
between two tensioned porous belts and squeezing out
the water as the sediment/belt "sandwich" passes over
and under various size rollers. All belt filter presses
incorporate the following features: a polymer conditioning
zone, a gravity zone, a low pressure zone, and a high
pressure zone. Polymer conditioning produces a super-
f locculation phenomenon that allows water to drain more
efficiently. The gravity drainage zone and the low pres-
sure zone prepare the sediment for the high pressure
zone, where most of the water removal actually takes
place.
Belt filter presses are common dewatering choices in
Europe and the United States. They can dewater sedi-
ment rapidly and do not take as large an area as the air
drying processes. Belt filter presses are thus often used
in confined locations (such as cities) and where large vol-
umes of sediment must be dewatered. They do not
dewater as completely as air drying processes, however,
and may be limited by the percent solid demands of the
treatment to be used. Furthermore, if the sediment is very
gritty, the belts may wear out rapidly.3
Chamber filter presses also use positive pressures, but
apply the pressure to the sediments inside rigid, individual
filtration chambers operated in parallel.
22
-------
Table 5-1. Summary of Dewatering Techniques7
Technique
Confined
Disposal
Facility
Belt Filter Press
Chamber
Filtration
Vacuum Rotary
Filtration
Solid Bowl
Centrifuge
Basket
Centrifuge
Gravity
Thickening
Applications
Dewatering sediment of any grain size
to a solids content of up to 60
percent and up to 99 percent solids
removal.
Generally used for large
scale dredging operations
where land space is available.
Used to dewater fine grained
sediments. Capable of obtaining
relatively dry filter cake containing up
to 45 to 70* percent solids; able to
achieve solids capture of 85 to 95%.
Generally best suited of filtration
methods for mobile treatment systems.
Used to dewater fine grained
sediments.
Capable of obtaining a relatively dry
filter cake with a solids content up to
50 to 80* percent; able to achieve a
high solids capture rate of up to 98%.
Used to dewater fine grained
sediments capable of obtaining a filter
cake of up to 35 to 40% solids and a
solids capture rate of 88 to 95%.
Thickening or dewatering sediments;
able to obtain a dewatered sludge with
15 to 35% solid; solids capture
typically ranges from 90 to 98%.
Suitable for areas with
space limitations.
Thickening or dewatering sediments;
able to obtain a dewatered sludge with
10 to 25% solids. Solids capture
ranges from 80 to 98%.
Suitable for areas with space
limitations.
Good for hard-to-dewater sludges.
Thickening of sediment slurries to
produce a concentrate that can then
be dewatered using filtration or
dewatering lagoons. Able to produce a
thickened product with a solids
concentration of 15 to 20%.
Limitations
Requires large land areas.
Requires long set-up time.
Labor costs associated with
removal or dewatering
sediments are high.
Systems using gravity drainage
are prone to clogging.
Systems using vacuums
require considerable
maintenance and supervision.
Systems based on electro-
osmosis are costly.
Performance is very sensitive
to incoming feed
characteristics and chemical
conditions.
Belts can deteriorate quickly in
presence of abrasive material.
Costly and energy intensive.
Replacement of filter media is
time consuming.
Least effective of the filtration
methods for dewatering.
Energy intensive.
Not as effective in dewatering
as filtration or lagoons.
Process may result in a build-
up of fines in effluent from
centrifuge.
Scroll is subject to abrasion.
Not as effective in dewatering
as solid bowl centrifuge,
filtration, or dewatering
lagoons.
Process may result in a build-
up of fines in effluent from
centrifuge.
Units cannot be operated
continuously without complex
controls.
Least effective method for
dewatering sediment slurries.
Requires use of a substantial
amount of land.
Secondary Impacts
Potential for
groundwater
contamination.
Potential for
localized odor
and air pollution
problems.
Generates a
substantial amount
of waste water
that must be
treated.
Generates a wash
water that must
subsequently be
treated.
Generates a wash
water that must be
treated.
No significant
secondary impacts.
No significant
secondary impacts.
Potential for
localized odor and
air pollution
problems.
Relative Cost
Low to High
Medium
High
High
Med. to High
Med. to High
Low to Med.
'Percent solids achievable may represent values for optimal conditions and do not necessarily represent normally expected values.
Dredged sediments are often fine-grained and difficult to dewater to the maximum indicated values.
23
-------
Vacuum rotary filtration uses negative pressure to pull the
water io the interior of a drum while the sediments adhere
to the exterior.
Centrifuges use the centrifugal forces created by a rapidly
rotating cylindrical drum or bowl to separate solids and
liquids based on variations in density. There are two types
of dewatering centrifuges: the solid bowl centrifuge and
the basket centrifuge.
Gravity thickening is accomplished in a continuous flow
tank. Sediments settle to the bottom and are removed by
gravity or pumping. Water overflows the tank and leaves
through an effluent pump. Gravity thickeners are used
primarily in tandem with other pre-treatment technolo-
gies; they reduce the hydraulic load to subsequent pre-
treatment options.
5.4 Particle Classification
Particle classification separates the slurry according to
grain size or removes oversize material that is incompat-
ible with subsequent processes. Classification by grain
size is important in the management of sediments con-
taminated with toxic materials since the contaminants
tend to adsorb primarily onto fine grain clay and organic
matter. The small grain solids of a specific size or less can
be treated while the relatively non-contaminated, coarser
soils and sediments can be disposed of with minimal or no
additional treatment. Separation technology for a given
site depends on the following: volume of contaminated
sediments; composition of the sediments, such as grada-
tion, percent clays, and percent total solids; characteriza-
tion of the contaminants; types of dredging or excavation
equipment used; and site location and surroundings,
including available land area. Particle classification op-
tions include screening processes that depend on size
atone, processes that depend on particle size and density
or density alone, and processes that depend on conduc-
tive or magnetic properties of the particles.1
Particle classification technologies include: impoundment
basins, hydraulic classifiers, hydrocyclones, grizzlies,
and screens. Following is a description of these technolo-
gies. Applications, limitations, and relative costs for the
first three listed particle classification technologies are
identified in Table 5-2.
Impoundment basins allow suspended particles to settle
by gravity or sedimentation. A slurry of dredged material
is introduced at one end of the basin; settling of solids —
depending on the particles' diameters and specific gravi-
ties —occurs as the slurry flows slowly across the basin.
The ftow resulting at the opposite end has a greatly
reduced solids content. Multiple impoundment basins in
a series can separate sediments across a range of sizes.
Hydraulic classifiers are rectangular tanks that function
similarly to impoundment basins. They have a series of
hoppers along the length of a tank which collects sedi-
ments of various sizes. Motor-driven vanes sense the
level of solids and activate discharge valves as the solids
accumulate in each hopper. Hydraulic classifiers may be
used in tandem with spiral classifiers to separate fine
grained materials such as clay and silt. Portable systems
that incorporate hydraulic and spiral classifiers are
available.
Hydrocyclones use centrifugal force to separate sedi-
ments. A hydrocyclone consists of a cone-shaped vessel
into which a slurry is fed tangentially, thereby creating a
vortex. Heavier particles settle and exit at the bottom
while water and sediments exit through an overflow pipe.
Hydrocyclones may be useful where a sharp separation
by particle size is needed.
Grizzlies are vibrating units reliable in the removal of
oversized material, such as bricks and rocks. Grizzlies
are very rugged and are useful in reducing the amount of
abrasive material in order to minimize wear on subse-
quent, more delicate, technologies.
Screens may be vibrating or stationary and operate by
selectively allowing particles to pass through them. As the
slurry passes over the screen, fine-grained particles and
water sift through the screen and larger particles slide
over the screen. Screens come in a variety of types with
a variety of applications to contaminated sediments,
5.5 Handling/Rehandling
^,
The amount of handling and rehandling required by
various pre-treatment options will also influence pre-
treatment decisions. Especially with severely contami-
nated sediments, all equipment that comes in contact with
the sediments will require subsequent decontamination.
For example, air drying heavily contaminated sediments
requires that the sediments be put in the drying structure
and later rehandled when the dewatered sediments are
removed in a more highly concentrated form. Rehandling
also mechanically disrupts the sediments and increases
the probability of introducing contaminants into the envi-
ronment. Conversely, a series of pre-treatment steps
requiring rehandling may be the most efficient way of
separating the contaminated sediments and preparing
them for treatment. For example, the Dutch are using
particle classification (hydrocyclones) and dewatering
(belts, filter presses, chamber filter presses, and others)
24
-------
Table 5-2. Summary of Sediment/Water Separation Techniques7
Technique
Impoundment Basin
Hydraulic Classifier
Hydrocyclones
'
Applications
Used to remove particles down
to a grain size of 20 to 30
microns without flocculants,
and down to 10 microns with
flocculants.
Provide temporary storage of
dredged material.
Allow classification of
sediments by grain size.
Used to remove particles from
slurries in size range of 74 to
149 microns (fine sand to
coarse sand).
Used to separate and classify
solids in size range of 2,000
microns or more down to 1 0
microns or less.
Limitations
Requires large land areas.
Requires long set-up time.
Hydraulic throughput is
limited to about 250 to
300 tph regardless of size.
Not capable of producing
a sharp size distinction.
Requires use of large land
area for large scale
dredging or where solids
concentrations are high.
Not suitable for dredged
slurries with solids
concentrations greater
than 1 0 to 20 percent.
Secondary Impacts
Potential for
groundwater
contamination.
No significant
impacts.
No significant
impacts.
Relative Cost
High
Med.
Med.
to improve the quality of dredged material prior to treat-
ment or disposal. Such a series is similartothe "treatment
train" described in Chapter Six.
Although methods of treatment are not addressed in this
document, the water generated during dewatering gener-
ally contains contaminants and suspended solids and
may require further treatment.
5.6 References
1. Averett, D.E., B.D. Perry, and E.J. Torrey. Re-
view of Removal, Containment and Treatment
Technologies for Remediation of Contaminated
Sediment in the Great Lakes. Miscellaneous
Paper EL90-25, U.S. Army Corps of Engineers,
Vicksburg, Mississippi, 1990.
2. USAGE. Confined Disposal of Dredged Material.
EM 1110-2-5027, U.S. Army Corps of Engineers,
September, 1987.
USEPA. Dewatering Municipal Wastewater
Sludges. EPA-625/1-87-014, U.S. Environmental
Protection Agency, Cincinnati, Ohio, September,
1987.
USEPA. Responding to Discharges of Sinking
Hazardous Substance. EPA-540/2-87-001, U.S.
Environmental Protection Agency, Cincinnati,
Ohio, September, 1987.
25
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-------
CHAPTER 6
TREATMENT TECHNOLOGIES
6.1 Introduction
Treatment technologies, for the purpose of this chapter,
are defined as those technologies that destroy, remove,
immobilize, isolate, or otherwise detoxify the contami-
nants in the sediments. The selection of a treatment
technology (or a train of technologies) is based on sedi-
ment characteristics, contaminant types, location, cost,
and prior and subsequent decisions in the remediation
sequence.
This chapter presents a logic for screening technologies
followed by a description of technologies by type. Tech-
nologies included in this chapter have all been at least
bench-scale tested on contaminated sediments. Tech-
nologies which potentially apply to sediments, but which
have not yet been tested, or which have been tested only
on soils, have not been included. Due to the rapid
advance of contaminated sediment remediation science,
the catalog of technologies included in this document
should not be viewed as exhaustive. Finally, primarily
because of the site-specific influence that sediments and
contaminants have on them, costs are not discussed in
this chapter.
6.2 Technology Screening Logic
The first step in selecting an appropriate remedial alterna-
tive is to determine treatment goals. In determining
treatment goals, questions of whetherto remediate a site
and what degree of cleanup is necessary should be
addressed. Once these questions are answered, meth-
ods to be used in achieving the desired remediation can
be determined.
6.2.1 Screening for Feasible Technologies
Contaminants and contaminant concentrations vary widely
between sites and within sites. Furthermore, there is
usually a high degree of variability among site character-
istics. Because of these sources of variability, selection
of appropriate and feasible remediation techniques for
contaminated sediments is a complex task. No simple
management plan or screening procedure exists for se-
lecting among available options. A screening logic is
needed that can take into account specific site factors, the
degree of protection required, costs, and availability and
reliability of cleanup alternatives. The Environmental
Protection Agency provides guidance on technology
screening in The Feasibility Study Development and
Screening of Remedial Action Alternatives.^ The follow-
ing section is a descriptio n of a tech nology screening logic
basedon the process usedforcontaminated sediments at
the New Bedford Harbor site, Massachusetts.
The fundamental steps in searchingforafeasibletechnol-
ogy to remediate a contaminated sediment are to: (1)
identify site and contaminant characteristics, (2) develop
a list of treatment options, and (3) conduct a defaifed
evaluationof the possible treatments. Stepone hasbeen
discussed irv Chapters One, Two* and Three and will not
be addressed here.
Step 2. The initial; list of treatment options shouldbe fairly
complete. Although this list may be somewhat cumber-
some,, technologies will be developing so rapidfy over the
next few years that a technology option should not be
dismissed unless it has received fair consideration. For
example, Allen and Ikaiainen presented a list of 56 poten-
tial treatment technologies that were grouped into four
general treatment classes (Table 6-t). This list was
developed to screen treatments for the New Bedford
Harbor siter parts of which are highly contaminated with
both PCBsand metals. In the initial screening, more than
half the treatments were eliminated because they would
not work with metals or organics in either a sediment or
water matrix?
Step 3. The detailed evaluation of the initial list should be
based on selected, appropriate criteria. For example,
Allen and Ikalainen's criteria were based on effective-
ness, implementation (engineering and control consid-
erations), and costs.2 This detailed evaluation will pro-
duce a short list of feasible and effective technologies.
27
-------
Table 6-1. Identification of Hazardous Waste Treatment Technologies
Considered for the Treatment of New Bedford Harbor Sediments2
TECHNOLOGY
Biological
Advanced Biological Methods
Aerobic Biological Methods
Anaerobic Biological Methods
Composting
Land Spreading
Physical
Air Stripping
Soil Aeration
Carbon Adsorption
Ftocculation/Precip'rtation
Evaporation
Centrifugation
Extraction
Filtration
Solidification
Granular Media Filtration
In Situ Adsorption
Ion Exchange
Molten Glass
Steam Stripping
Supercritical Extraction
Vitrification
Partide Radiation
Microwave Plasma
Crystallization
Diaiysls/Electrodialysis
Distillation
Resin Adsorption
Reverse Osmosis
Ultrafiltration
Acid Leaching
Catalysis
Chemical
Alkali Metal Dochlorination
Alkaline Chlorination
Catalytic Dehydrochlorination
Electrolytic Oxidation
Hydrolysis
Chemical Immobilization
Neutralization
Oxidation/Hydrogen Peroxide
Ozonation
Polymerization
Ultraviolet Photolysis
Thermal
Electric Reactors
FlukJized Bed Reactors
Fuel Blending
Industrial Boilers
Infrared Incineration
In Situ Thermal Destruction
Liquid Injection Incineration
Molten Salt
Multiple Hearth Incineration
Plasma Arc Incineration
Pyrorysis Processes
Rotary Kiln Incineration
Wet Air Oxidation
Supercritical Water Oxidation
Sediment
Matrix
Yes
No
Yes
Yes
Yes
No
Yes
No
No
Yes
Yes
Yes
Yes
Yes
No
Yes
No
No
No
Yes
Yes
No
No
No
No
No
No
No
No
Yes
No
Yes
No
No
No
No
Yes
Yes
Yes
No
Yes
No
Yes
Yes
No
No
Yes
No
No
No
Yes
No
Yes
Yes
No
Yes
Water
Matrix
No
Yes
No
No
No
Yes
No
Yes
Yes
Yes
No
No
No
No
Yes
No
Yes
No
Yes
No
No
No
No
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
Yes
No
No
Yes
No
No
No
No
No
No
No
No
No
No
No
No
Yes
No
No
Yes
Yes
For PCB
Treatment
Yes
No
No
No
No
No
No
Yes
Yes
No
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
Yes
No
Yes
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
For Metal
Removal
No
No
No
No
No
No
No
No
Yes
No
No
No
No
Yes
Yes
No
Yes
No
No
No
Yes
No
No
No
No
No
Yes
Yes
No
Yes
No
No
No
No
No
No
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
28
-------
The detailed evaluation of technology options also re-
quires a system for ranking the options within the identi-
fied criteria. Unfortunately, a universal quantitative rank-
ing system is not possible. The reasons for this include:
necessary assumptions made regarding the applicability
of most alternatives, widely varying knowledge about the
performance of some alternatives in terms of the specified
criteria, how to consider tradeoffs between different alter-
natives, and the fact that different individuals or commit-
tees will rank the criteria for a given alternative differently.3
Carpenter reported a comprehensive technology screen-
ing and ranking procedure for PCB contaminated sedi-
ments. Approximately 20 technologies were evaluated
that fitted into six general classifications (low-temperature
oxidation, chlorine removal, pyrolysis, removal and con-
centration, vitrification, and microbial degradation). Keep-
ing in mind the rapid development of treatment technolo-
gies, it is still appropriate to note that at that time, the only
proven technology available was believed to be dredging
and incineration.4
6.2.2 Treatment Train Approach
The "treatment train approach" is a valuable concept for
remediating contaminated sediments. Taking such an
approach acknowledges the complexity of dealing with
contaminated sediments and the fact that a multifaceted
approach, combining several technologies into a se-
quence of steps, may permit more flexibility in addressing
problems. In many cases, a treatment train may be
essential to clean up sediments containing different types
of contaminants. For example, in their work on screening
technologies suitable for New Bedford Harbor, Allen and
Ikalainen reported eliminating a number of methods
because these specific technologies could not deal with
both organics and metals.2 With a treatment train ap-
proach, it may be possible to effectively couple two or
more technologies to successfully address a contamina-
tion problem where no single technology would perform
satisfactorily.
Technologies coupled in a treatment train should be
evaluated for more than just their ability to address
specific contamination problems. The complementary
nature of technologies should be considered. For ex-
ample, in a hypothetical sediment contaminated with
metals and PCBs, dewatering might be done to prepare
the sediment for a metal extraction process. While the
dewatering and metals extraction process may do little to
remove PCBs, they may make the sediment a suitable
candidate for destruction of the PCBs through incinera-
tion. In this train, the lowered water content of the
sediment reduces incineration costs, while the reduction
of metals in the sediment simplifies treatment of incinera-
tion off-gases.
Currently, most technologies for the remediation of con-
taminated sediments are goingto require dredging. Thus,
the key sequence of events in a treatment train approach
will very likely include the following: dredging, transport,
possible pre-treatment, treatment, post-treatment (includ-
ing possible treatment of off-gases or waste-water), and
placement of the cleaned material.
A treatment train approach was tested at the bench-scale
level on sediments contaminated with both metals and
organics from the Halby Chemical site in Wilmington,
Delaware. Low temperature thermal desorption was
evaluated as a pre-treatment step to remove compounds
that may impede the solidification/stabilization process.
While it did successfully remove most volatile and semi-
volatile compounds, results indicated that low tempera-
ture thermal desorption may not be needed as a pre-
treatment step prior to solidification/stabilization for these
sediments.5
The Dutch bench-tested a treatment train approach in-
volving solvent extraction and biodegradation of sedi-
ments contaminated with PAHs. Results indicated that
when preceded by hydrocyclone separation, the overflow
could be treated by basin aeration (a biodegradation
method) and the underflow could be treated in one of
three ways: by solvent extraction with triethylamine (TEA)
if heavily contaminated; by biodegradation if the contami-
nants are not too strongly sorbed to sediment particles;
and by reuse without further treatment if not polluted.6
In summary, because of the inability of most technologies
to treat more than one type of contaminant, the concept of
a treatment train approach utilizing several technologies
in sequence may add the flexibility needed to make many
projects feasible and more cost effective.
6.2.3 Side Stream
The term "side stream" refers primarily to the need to
address contaminants generated by primary technolo-
gies. Whereas incineration may effectively destroy the
organic contaminants in dredged material, the off-gases
and/or ash may contain other types of contaminants.
Thus, side stream treatment may be required to further
treat contaminants collected. Presumably, these side
stream products would be more easily treated by methods
which are more conventional and less costly than the
technology required to clean the sediments initially.
Necessary side stream technologies would be part of the
overall evaluation for a remediation approach.
29
-------
6.3 Extraction Technologies
Extractive treatment technologies remove organic or
metallic contaminants from sediments but do not destroy
or chemically alter the contaminant. Effluent streams will
be much more concentrated with the contaminant than
was the original sediment. Extractive treatmenttechnolo-
gies should be viewed as one part of a treatment train
since organic contaminants still need to be destroyed
after extraction. The contaminant-rich effluent from ex-
traction technologies can be treated by any of a number
of thermal, physical/chemical, and/or biological treatment
technologies. By concentrating the contaminants in a
smaller volume of sediment or residual, a significant cost
savings may be realized.
Traditionally, the term "extraction" has referred to chemi-
cal extraction, but as used here it refers to a larger group
of technologies that essentially achieve volume reduction
by removing a contaminant from a waste stream and then
concentrating it. For example, soil washing is usually
thought of as being separate from chemical extraction,
but using the present definition, soil washing is consid-
ered an extraction technology.
Extraction technologies may have application for the
treatment of contaminated sediments. The large volume
of material to be treated coupled with the relatively low
concentration of contaminants make technologies ca-
pable of volume reduction and the concentration of con-
taminants attractive.
6.3.1 Chemical Extraction
Chemical extraction involves removing contaminants from
sediment by dissolution in a solvent that is later recovered
and treated. A variety of chemical extraction processes
exist and they employ a number of solvents. Solvents are
chosen based on contaminant solubility and on whether
the contaminant is organic or inorganic.
CF Systems Organic Extraction Process. CF Systems
Corporation has developed a critical fluid solvent extrac-
tion with liquified gas technology that has been applied in
pilot scale studies to contaminated sediments (Figure 6-
1). Liquified gases (propane and/or butane) at high
pressure are used to extract oils and organic solvents
from sediments in a continuous process. After contact
with the sediment, the contaminated solvent enters a
separator where the pressure is reduced and the solvent
is decanted from the oil phase. The solvent is then
compressed and recycled. Materials that are primarily
contaminated with heavy metals or inorganic compounds
are not appropriate for this technology.
CF Systems Organic Extraction Process was demon-
strated under EPA's Superfund Innovative Technology
Evaluation (SITE) program at the New Bedford Harbor
site, Massachusetts. The site was listed on the National
Priority List (NPL) because PCB concentrations in the
sediment ranged from 50 ppm to 30,000 ppm. The
sediment treated in the extraction process was 30-40
percent solids, of which 37 percent was sand, 41 percent
was silt, and 22 percent was clay. Table 6-2 shows the
percent reduction in PCB feed concentration from each of
the demonstration tests.
Basic Extraction Sludge Treatment (BESTV. The BEST
process, developed by Resources Conservation Com-
pany, is an extraction process capable of treating sedi-
ment contaminated with PCBs, hydrocarbons, and other
high molecular weight organics. The process contacts
one part sediment with one to seven parts of a secondary
or tertiary amine, usually triethylamine (TEA). The ex-
traction step takes place at near ambient temperatures
and pressures and at a pH of 10. Under these conditions
TEA is simultaneously miscible with oil and water. The ex-
tracted solids are removed by centrifugation and then
dried to remove residual TEA. The contaminant rich liquid
phase is heated, reducing the TEA solubility in water. The
resulting TEA/oil phase is decanted from the water phase.
The TEA/oil phase is sent to a stripping column where the
TEA is recovered and the oil is discharged. The water
phase is also sent to a stripping column to remove
residual TEA (Figure 6-2).
Compressor
Recycled Solvents j[
Solvent
Feed
Extr
actor
Solids
Figure 6-1. CF Systems Organic Extraction Process
Source: CF Systems Corporation
30
-------
Table 6-2. Demonstration Test Results of CF Systems Organic Extraction Process6
Test Number
2*
3
4
5
Number
of Passes
10
3
6 ,.
3
PCB
Feed Cone.
350
288
2575
.- . , ...
Percent
Reduction
89 percent
72 percent
92 percent
Decontamination
Test #1 was the shakedown test.
Raw Waste
r
Frontend
Neutralization
L. -J
Power
Water
Peripheral
Utilities
-•-J j . Instn.
1
Steam ^^
Cooling Water
. Instrumentation Air
Site Specific
Figure 6-2. BEST Chemical Extraction Process
Source: Resources Conservation Company
Bench-scale treatability studies of the BEST process
were conducted on lagoon sediments from the Arrow-
head Refinery Superfund site in Hermantown, Minnesota.
The sediments were contaminated with both metals and
organics. Results showed that the BEST process suc-
cessfully separated the contaminated wastes into three
fractions: aqueous, oil-containing organics, and solids.
Due to process difficulties in handling metals, lead was
found in both the oil and solid fractions. Other bench-
scale tests conducted on a variety of sediments indicated
PCB removals of 96 percent in all cases and better than
99 percent in most cases.7
Inaprocesssimilarto the BEST process, TEA was bench-
tested in the Netherlands as an extraction solvent for the
removal of PAHs from sediments. Results indicated
removal efficiencies of 90-99 percent and that several
extraction steps may be necessary to increase efficiency.
Toluene was also tested as an extraction solvent, but was
not as efficient as TEA.6
Low Energy Extraction Process (LEEP). The LEEP is
being developed in conjunction with Enviro-Sciences,
Inc., by Applied Remediation Technology. It uses a
hydrophilic leaching solvent to extract organic contami-
nants from sediments and then concentrates the contami-
nants in a hydrophobic stripping solvent. Advantages
include conversion of a high-volume, solidwaste stream
to a low-volume, liquid waste stream, operation at ambi-
ent conditions with low energy requirements, and use of
simple processes and equipment. Disadvantages in-
clude necessary further treatment of the solvent stream
and the contaminant specific nature of the selected leach-
ing solvent. Bench-scale tests conducted on sediments
from Waukegan Harbor, Illinois reduced PCB concentra-
tions from 3200 ppm to 1 ppm. Plans exist to test a pilot-
scale unit capable of treating 30 to 50 tons/hour.9
31
-------
Acetone Extraction. Acetone has been successfully used
by the Department of Defense (DOD) to remove explo-
sives (TNT, DNT, etc.) from sediments. Unfortunately,
this process concentrates the acetone-dissolved explo-
sives in an enclosed container and may be very danger-
ous.10 For this reason, acetone extraction was aban-
doned in favor of rotary kiln incineration (see Rotary Kiln
Incineration below).
Low Temperature Thermal Stripping fLTTS). LTTS con-
sists of indirectly heating the contaminated sediment to
250-800°F in an effort to volatilize contaminants and
thereby remove them from the solid matrix. Volatilized
organic contaminants subsequently pass through a car-
bon adsorption unitorcombustion afterburnerfordestruc-
tion. LTTS systems generally may be used to remove
volatile organic compounds from sediments. The system
will be ineffective in removing metals and high boiling
point organics. Feeds with a high moisture content (>60
percent) may require dewatering prior to treatment in
order to make LTTS economically feasible. The high
moisture content increases energy requirements and
reduces the process throughput rate (see Figure 6-3).
Bench-scale tests of contaminated sediments from the
Halby Chemical site in Wilmington, Delaware indicated
that LTTS successfully removed most volatile and semi-
volatile compounds at temperatures between 300° and
500°F with between 15 and 30 minutes residence time.5
AIR TO
ATMOSPHERE
HOT at
Mscnvon
\
Figure 6-3. Low Temperature Thermal Stripping
Source: U.S. Army Toxic and Hazardous Materials
Agency. Aberdeen Proving Ground.
6.3.2 Soilwashing
Soil washing is a water-based, volume reduction process
in which contaminants are extracted and concentrated
into a small residual portion of the original volume using
physical and chemical means. The principal process
involvestransferofthecontaminantsfromthesedimentto
the wash water and their subsequent removal from the
water. The small volume of contaminated residual con-
centrate is then treated by destructive or immobilizing
processes. By changing steps in the process, soil wash-
ing may be made amenable to a variety of site character-
istics.
Full-scale commercial soil washing plants have been
operating in Europe since 1982. Seventeen plants are
currently in operation, nine devoted solely to contami-
nated sediment remediation. Depending on the size of
the facility, these plants are capable of handling from 10-
130 tons of soil or sediment/hour. Contaminants treated
by these plants include metals and a variety of organics,
but individual plants are limited in their ability to handle
certain contaminants. EPA also found that the effective-
ness of the European soil washing plants may be limited
at certain sites by the size of particles they rejected
(particle classification is an early step in the European soil
washing process).11
6.4 Destruction/Conversion
Destruction and conversion technologies attempt to trans-
form organic contaminants into the relatively benign end
products resulting from thermal or chemical destruction or
bacterial metabolism. While metals are difficult for these
technologies to handle, some options do concentrate
metals into a waste product (e.g., slag or plant biomass)
that makes subsequent disposal simpler. However,
sediments that are contaminated with both organics and
metals may require pre-treatment or careful disposal of
wastes.
6.4.1 Thermal Destruction
The applicability of a number of thermal processing meth-
ods on sediments has already been demonstrated in
private and government sponsored cleanups. Although
incineration and other thermal technologies have been
shown to be among the most effective treatment tech-
nologies for hazardous and toxic waste destruction, costs
may be high for sediments due to the intensive energy
requirements for burning materials with high water con-
tents and due to regulatory requirements for the subse-
quent disposal of ash and slag.
32
-------
Ideally, the ultimate goal of thermal destruction is to
convert waste materials into benign end-products (CO2>
H20 vapor, SO2, NOX, HCI, and ash). Temperatures may
range from 300°F to over 1650°F. In high temperature
applications where strong oxidation is involved, the use of
50-150 percent excess air is not uncommon.
The suitability of contaminated sediments for the applica-
tion of thermal treatment processes is determined by the
physical and chemical makeup of the material and the
volume to be treated. These characteristics impact:
1. The extent of particle classification required.
2. The amount of dewatering required and the
selection of a dewatering method.
3. The type of thermal treatment utilized.
4. Air pollution control system design.
5. Treatment of residual ash prior to final disposal.
Pre-treatment options (#1 and #2 above) were discussed
in Chapter Five. Thermal treatment side streams (#4and
#5) and thermal treatment options (#3) are described
below.
Thermal treatment side streams may require additional
treatment. The bottom and fly ash produced from incin-
eration is likely to contain some residual heavy metals and
may require further management. This may substantially
increase the cost of the soil/sediment treatment process;
however, recent tests conducted on slags obtained from
a rotary kiln (which handled all types of hazardous wastes
from around the Netherlands) indicated that up to 80
percent of the slags tested did not require further manage-
ment.12 The off-gases from sediments incineration gen-
erally require venturi- or injector-type scrubbers, ionizing
wet scrubbers, fabric filters or baghouses, or electrostatic
precipitators.13-14
Types of processes used to thermally remediate sedi-
ments include rotary kiln incineration, infrared incinera-
tion, circulating bed combustion, and vitrification. Gener-
ally, treatment methods with higher temperatures are
required for contamination consisting of high concentra-
tions of recalcitrant organics, such as PCBs. Due to
varying site characteristics and regulatory requirements,
selection of the best thermal treatment system should be
based on projected technical performance as assessed
from field pilot tests.
Rotary Kiln Incineration. A rotary kiln incinerator is a
cylindrical, refractory-lined shell that is fueled by natural
gas, oil, or pulverized coal. The kiln rotates to create
turbulence and, thus, improve combustion. This thermal
process is capable of handling a wide variety of solid
wastes, with residence times ranging from a few seconds
to hours for bulk solids. Combustion temperatures range
from 1200-3000°F.15
Rotary kiln combustion is amenable to sediments con-
taminated with organics. Prior to being fed into the kiln,
oversized debris and drums must be crushed or shred-
ded. Waste characteristics that are not suited for rotary
kiln systems include high inorganic salt content which
causes degradation of the refractory and slagging of the
ash, and high heavy metal content which can result in
elevated emissions of heavy metals which are difficult to
collect with afr pollution control equipment.
Rotary kiln incineration has been used at two sites by the
Department of Defense (DOD) to decontaminate sedi-
ments contaminated with explosives (TNT, DNT, etc.).
These sites were at ammunition plants near Grand Island,
Nebraska and Shreveport, Louisiana.16 Two additional
ammunition plants, near Savannah, Illinois and Childers-
burg, Alabama are presently undercontraet to be cleaned-
up via rotary kiln incineration. Pilot studies have already
been conducted at the Savannah, Illinois site.
In the Netherlands, several companies have been oper-
ating commercial soil and sediment cleaning plants. For
example, NBM Bodemsanering BV has been operating a
plant since 1986. At this plant, contaminated soils and
sediments are incinerated in a rotary tube furnace.
Dewatering and particle screening precede incineration;
treatment of off-gases and waste-water follows incinera-
tion. The plant cleans soils and sediments to the satisfac-
tion of Dutch regulations. The plant has a maximum
capacity of 15 tons/hour under optimal conditions, and an
annual capacity of 85,000 tons.
Over the next ten years, this thermal process is to be
implemented on a full scale to remediate approximately
500,000 cubic meters (653,970 CY) of dredged sedi-
ments from the Neckar River in Germany. Conditions at
the Neckar River site demand that sediments be removed
on a regular basis. Additionally, a method for recycling
these cadmium contaminated sediments was devised.
The overall process involves the conversion of the mate-
rial into spherical aggregate forthe productionof masonry
blocks and lightweight concrete. The steps in the process
involve dewatering via a screen belt press, mixing of the
sediments with clay and additives, palletizing the mixture,
and then thermally processing in a rotary kiln at tempera-
tures of 2100°F. The end product is an expanded clay of
various sizes (0-16 mm) with a high compressive strength
and excellent insulation properties. The cadmium boils off
during incineration and is captured in the off-gas treat-
ment process.17
33
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Infrared Incineration. Infrared incineration systems are
designed to destroy solid hazardous wastes through
tightly controlled process parameters using infrared energy
as the auxiliary heat source. This system consists of a
rectangular carbon steel box lined with layers of a light-
weight, ceramic fiber blanket. Infrared energy, provided
by silicon carbide resistance heating elements, is used to
bring the organic wastes to combustion temperature (500
- 1850°F) for residence times of 10 -180 minutes. The
remaining organics are destroyed in a gas-fired chamber,
using temperatures of 1000 - 2300°F at residence times
of approximately 2 seconds.18-19
Full-scale tests of the Shirco Infrared System have been
conducted on lagoon sediments from the Peak Oil Super-
fund site In Brandon, Florida. The sediments were con-
taminated with metals, PCBs, and other organics. Lead in
the ash failed to pass the EP Toxicity Test, but it did pass
the TCLP. All organic compounds in the ash were below
regulatory limits.20 Available data suggest that this proc-
ess is suitable for solid wastes containing particles from 5
microns to 2 inches in diameter and having up to a 50
percent moisture content, which would suggest that this
process is conducive to the handling of sediments.
Circulating Bed Combustion (CBC^. The CBC is an
outgrowth of conventional f luidized bed incineration, which
is primarily applicable to homogeneous sludges and
slurries. This treatment process is capable of treating
solids, sludges, slurries, and liquids; the high degree of
turbulence and mixing caused by air velocities of up to 20
feet/second ensures treatment of a wide variety of wastes
at temperatures below 1560°F. Retention times range
from 2 seconds for gases to approximately 30 minutes for
largerfeed materials (less than one inch). A CBC devel-
oped by Ogden Environmental Services, Inc. has treated
PCB contaminated sediments from the Swanson River
Oil Field, Alaska in field demonstrations. This technology
is well-suited for materials with relatively low heating
values.21-22-23
Vltrificatton. Vitrification is a process in which hazardous
wastes are subjected to very high temperatures and
converted into a glassy substance. Organic contami-
nants are destroyed by the heat and inorganic contami-
nants are immobilized in the glass. Vitrification is poten-
tially applicable for a wide range of organic and inorganic
contaminants.
In situ vitrification (ISV) is a vitrification process in which
joule heating occurs when a high current of electricity is
passed through graphite electrodes inserted in the soil.
The resulting heat melts the soil, destroying organic
contaminants and incorporating inorganic contaminants
in the melt. As the melt cools, it forms an obsidian-like,
leach-resistant glass. Engineering scale tests have been
performed on PCB contaminated sediments from New
Bedford Harbor which indicate destruction and removal
efficiencies of greaterthan 99.99999 percent for organics
following off-gas treatment. TCLP testing resulted in
leach extract that contained metal concentrations below
the regulatory limits.24-25 One disadvantage of ISV is that
the process is not efficient for sediments with a high water
content and, thus, contaminated sediments may have to
be dredged and dewatered Alternatively, dikes may
isolate the contaminated sediments from the aquatic
environment and thus enable the subsequent implemen-
tation of ISV. The process may also be limited by site
characteristics. For example, large volumes of barrels
tend to cause short circuits.
6.4.2 Chemical Conversion
Chemical destruction technologies chemically transform
a toxic chemical into a relatively benign product. Few of
these technologies have been applied to the remediation
of contaminated sediments. Nucleophilic substitution will
be the only technology described here.
Nucleophilic Substitution. Nucleophilic substitution uses
a nucleophilic reagent to dechlorinate aromatic, organic
compounds, such as PCBs and dioxins, in a substitution
reaction. Common reagents include alkali metals in
polyethylene glycol (APEG) or in polyethylene glycol
methyl (APEGM). Proper control of temperature and
reaction time maximizes process efficiency. Tempera-
ture and reaction time are site-specific characteristics and
should be determined by prior testing. Nucleophilic
substitution requires dewatering of sediments.26
The Galson Research Corporation tested a nucleophilic
substitution process on PCB contaminated sediments
from New Bedford Harbor. The process they tested used
potassium hydroxide and polyethylene glycol (KPEG).
Dimethyl sulfoxide (DMSO) served as a phase-transfer
catalyst to promote PCB extraction. Bench-scale studies
of the KPEG showed reduction of 6,000 to 7,500 ppm
PCBs to 4 ppm in 12 hours at 165°C and residual recovery
of 98 percent.27
6.4.3 Biodegradation
Biological degradation is the conversion of organic wastes
into biomass and harmless metabolic byproducts, such
as CO2, CH4, and inorganic salts. Microorganisms (prin-
cipally bacteria and fungi) make up the most significant
group of organisms involved in biodegradation. The rate
34
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of contaminant biodegradation is determined by the
following: -
1. The presence of appropriate microorganisms.
2. Adequate concentrations of essential nutrients.
3. The availability and concentration patterns of the
compound to be degraded.
4. Contaminant effects on microbial population
activity.
Heavy metals in the slurry can inhibit biodegradation. For
that reason, a pre-treatment step to remove or decrease
the concentration of such inhibitors may be needed.
Methods for pre-treatment may consist of soil washing,
metal extraction, and biological treatment utilizing algal
cells in silica gel medium to remove heavy metals.
There are many bench-scale studies of biodegradation,
but fewfield applications to contaminated sediments. The
transition from the laboratory to the field is very difficult
because acclimation of microorganisms is much easier in
the laboratory.
The biodegradation of contaminated sediments can be
done by removing the contaminated sediments and then
treating or by leaving the sediments in place and treating
in situ.
Removal and Treatment. Removal allows three types of
biodegradation treatment processes: composting, bi-
oslurries, and solid phase treatment. A near-site biode-
gradation process that treats the contaminated sedi-
ments on barges near the removal site will be described
separately.
Composting involves the storage of highly biodegradable
and structurally firm materials such as chopped hay or
wood chips mixed with a 10 percent or less concentration
of biodegradable waste. There are three designs for
aerobic compost piles: the open windrow system, the
static windrow system, and in-vessel composting. In-
vessel composting may also be anaerobic; anaerobic
conditions are maintained by flushing the vessel with
nitrogen. Anaerobic efficiency appears to be less than
that obtained using aerobic vessels. Laboratory tests
conducted by Dutch researchers of an aerobic system in-
dicated that the total quantity of oxygen supplied may be
more important than frequency of aeration.6
Composting is relatively insensitive to toxic impacts on
microbes. Field demonstrations of composting for the
remediation of lagoon sediments contaminated with TNT
have been conducted at the Louisiana Army Ammunitions
Plant. Results indicated that contaminant concentrations
decreased from 12,000 ppm to 3 ppm.28
Bioslurries treat the contaminated sediment in a large
bioreactor. The system is designed to maintain intimate
mixing and contact of the microorganisms with the haz-
ardous waste compounds. The slurry is mechanically
agitated in a reactor vessel to keep the solids suspended
and to maintain the appropriate reaction conditions.
Additives such as inorganic and organic nutrients, oxy-
gen, acid or alkali for pH control, or commercial prepara-
tions of microorganisms may be necessary. A typical soil
slurry feedstock contains approximately 50 percent solids
by weight. Dissolved oxygen levels must be maintained
and temperatures should be stabilized to range between
60-160°F. Biodegradability of the pollutants, the sedi-
ment matrix, and the characteristics of the contaminant(s)
dictate retention time.
Another bioslurry method for treating dredged sediments
utilizes anaerobic digesters. These are air tight reactor
vessels with provisions for venting or collecting methane
and carbon dioxide. A methanogenic consortia (found in
anaerobic digesters or sewer sludge digesters) does the
work. The consortia consists of four different bacterial
groups, each of which metabolizes a different class of
compounds.
Bioreactors were studied at the bench-scale level in the
Netherlands. Results from these fourteen day batch
studies indicated removal efficiencies ranging from 82-95
percent for cutting oil and other organics in loam and
loamy sand.11 Other research by the Dutch indicated that
bioreactors had higher degradation rates than either land
farming or aerated basins.6
Solid phase treatment, or land farming, has now been
limited under the recently promulgated RCRA land dis-
posal restrictions to the handling of RCRA wastes in lined
land treatment units with leachate collection systems or in
RCRA permitted tanks. The dredged materials are lifted
into this prepared treatment unit. Land treatment is ac-
complished by adding nutrients (nitrogen and phospho-
rus) and exogenous microbial additives and by tilling the
sediments to facilitate the transport of oxygen through the
migration system.
Wastes are typically mixed to a depth of 6 to 12 inches,
where the biochemical reactions take place. Tillage meth-
ods are more useful for materials containing higher con-
centrations of soils but will take more time to obtain target
concentrations levels of pollutants than a bioslurry proc-
ess. Treated soils must be delisted, if RCRA wastes were
remediated.9
A near-site process developed by Bio-Clean requires
dredging and subsequent treatment of the sediment in a
series of nine processing units on barges, thus eliminating
35
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the need for transportation of contaminated sediments to
a distant treatment site. The process uses naturally-
occurring bacteria to aerobically degrade organic con-
taminants. The batch process involves the extraction,
sterilization, and soiubilization of the contaminants utiliz-
ing high temperature, high pH, and biodegradation.26
In Silu Biodegradation. In situ biodegradation has cap-
tured regulators'attention because leaving the sediments
in place can limit the negative environmental impacts
caused by dredging. In situ biodegradation relies on
indigenous or introduced aerobic or anaerobic bacteria to
degrade organic compounds in soils. Bioavailability is the
key to successful in situ biodegradation. Sediment prop-
erties which impact bioavailability influence the interac-
tion between sediment and contaminants. Such proper-
ties include type and amount of clay, cation exchange
capacity, organic mattercontent, pH, the amount of active
iron and manganese, oxidation-reduction conditions, and
salinity.a The important site characteristics to be identi-
fied for in situ biodegradation are listed below:29
1. Characterization and concentration of wastes,
particularly organics in the contaminated sedi-
ments.
2. Microorganisms present in the sediment and
their capability to degrade, co-metabolize, or
absorb the contaminants.
3. Biodegradability of waste constituents (half-life,
rate constant).
4. Biodegradation products.
5. Depth, profile, and areal distribution of constitu-
ents in the sediments.
6. Sediment properties for biological activity (such
as pH, oxygen content, moisture and nutrient
contents, organic matter, temperature, etc).
7. Sediment texture, water-holding capacity, de-
gree of structure, erosion potential of the soil.
8. Hydrodynamics of the site.
This form of treatment impacts both the sediments and
surface water. Examples of disadvantages of in situ
btodegradation include: (1) the technique is not suitable
for soil contaminated with metals present in inhibitory
concentrations; and (2) iron fouling can inhibit oxygen
availability.
Research over the last decade suggests that naturally
occurring bacteria may be able to biodegrade PCBs. Two
separate and complementary degradation pathways are
involved in the natural destruction of PCBs. In one
pathway, anaerobic bacteria remove chlorine atoms from
PCBs by reductive dechlorination. In the other pathway,
aerobic bacteria destroy lightly chlorinated PCBs.30'31
Both pathways have been documented in sediments and
in laboratory studies, but they have not been shown to
occur in sequence within the same natural system.32
Current research focuses on linking these pathways in the
laboratory, increasing the rate of degradation in each
pathway, and in moving from bench-scale to field-scale
demonstrations.
The most common in situ biodegradation process is
enhancement of natural biochemical mechanisms for
detoxifying or decomposing the soil contaminants. Ex-
amples of enhancement include increasing the sediment's
dissolved oxygen levels (for aerobic degradation), pro-
viding alternative electron acceptors, enriching sediments
with auxiliary carbon sources, and mixing the sediments
to improve bacterial access to contaminants.
6.5 Containment
Containment is the immobilization and/or isolation of
contaminated sediments. Solidification/stabilization is
one type of containment option based on immobilization.
Chaptei VII describes disposal alternatives that provide
containment by isolation.
6.5.1 Solidification/Stabilization
Solidification/stabilization refers to the use of additives or
processes to transform hazardous waste into a more
manageable or less toxic form by immobilizing the waste
constituents. By producing a solid from a liquid or slurry,
solidification/stabilization technologies improve the han-
dling characteristics of the material, decrease the surface
area from which contaminant transport may occur, and
limit the mobility of a contaminant exposed to leaching
fluids. Types of solidification/stabilization technologies
include:33
1. Cement-based solidification/stabilization.
2. Pozzolonic solidification/stabilization.
3. Thermoplastic solidification/stabilization.
4. Organic polymerization solidification/stabilization.
5. Organophilic clay-based solidification/stabiliza-
tion processes.
Solidification/stabilization functions both physically and
chemically. Solidification is a physical process which
refers to the conversion of a liquid or semi-solid to a solid.
Solidification is considered an effective process in the im-
mobilization of both metals and inorganics. Stabilization is
a chemical process which refers to the alteration of the
chemical form of contaminants. Generally, stabilization is
considered an effective process in the immobilization of
36
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metals, but not organics. In fact, organics may actually
interfere with solidification/stabilization setting reactions.34
The applicability of solidification/stabilization processes
to the sediments of concern is determined by chemical
and physical analysis. Several leach tests are available
for this purpose. Listed wastes requires the Toxicity
Characteristics Leaching Procedure (TCLP). Additional
leaching tests may be chosen from American National
Standards Institute (ANSI) procedures appropriate forthe
contaminant. Newer procedures, such as the Standard
Batch Leachate Test (SBLT), are constantly being re-
viewed and accepted according to the need or circum-
stance.33
Physical testing, aimed at such product characteristics as
bearing capacity, trafficability, and permeability, is ac-
complished through established engineering tests. For
example, ratios of waste to binder in each system are
evaluated using the Unconfined Compressive Strength
(UCS) Test. Bulk density, permeability, and moisture
content are also commonly tested to determine the de-
gree of solidification/stabilization.
6.5.2 Sediment Applications of Solidification/
Stabilization
Following is a brief discussion of solidification/stabiliza-
tion technology applications for contaminated sediments.
Marathon Battery. Bench-scale and pilot-scale tests were
conducted to evaluate the application of solidification/
stabilization at the Marathon Battery Company site in the
Village of Cold Spring, New York.35 Between 1952 and
1979 hydroxides of cadmium, nickel, and cobalt were
discharged into a marsh and a cove by the Marathon
Battery Company. The feasibility study considered solidi-
fication/stabilization as an option.
Tests were conductedto conf irmwhethercadmium, cobalt,
and nickel could be chemically stabilized or physically
bound to the sediments to levels below the RCRA EP
toxicity test limits. Three mixtures of waste and pozzolan
and lime and three mixtures of waste and portland cement
were tested. After 48 hours, two of the pozzolan and lime
mixtures passed the RCRA EP toxicity test, but only one
of the portland cement mixtures passed the RCRA EP
toxicity test. Based on these limited laboratory results,
sediment metals such as cadmium, cobalt, and nickel
appeared to be immobilized.
New Bedford. The application of solidification/stabiliza-
tion technology forthe treatment and disposal of contami-
nated materials was tested at the bench-scale level at the
New Bedford Harbor Superfund project.36 The Upper
Acushnet River Estuary in New Bedford, Massachusetts
is contaminated by PCBs and heavy metals. Dredged
samples were solidified and stabilized with Type I port-
land cement and a portland cement/proprietary reagent in
three formulations.
Unconfined compressive strength was the key test for
assessing physical solidification; batch leach tests using
distilled-deionized water were the key tests for assessing
chemical stabilization. Leachates, solidified and stabi-
lized sediment, and untreated sediment samples were
analyzed for concentrations of PCBs and metals, includ-
ing cadmium and zinc. Unconfined compressive strength
was 20 to 481 psi indicating a strong versatility for solidi-
fication. Batch leach tests showed that the chemical
stabilization of the three formulations was similar. The
teachability of cadmium and zinc was eliminated or sub-
stantially reduced. Leaching of PCBs was reduced by 10
to 100 times. However, copper and nickel were more
readily mobilized after treatment.36
Indiana Harbor. The navigation channel at Indiana Har-
bor in northwestern Indiana is contaminated by metals,
PCBs, and other organic contaminants. A study was
conducted by the Environmental Laboratory, Department
of the Army, Vicksburg, Mississippi to evaluate alternative
methods for dredging and disposing of the contaminated
sediments.37
Composite samples were tested and compared with
Indiana water quality standards and EPA federal water
quality criteria. The solidification/stabilization processes
selected for this study were portland cement, portland
cement with fly ash, portland cement with fly ash and/or
sodium silicate, fly ash with lime, and various mixtures of
proprietary polymers.
Unconfined compressive strength was used as a key
indicator of physical solidification. The range in a 28-day
unconfined compressive strength test was 48.5 psi to 682
psi for processes not involving sodium silicate. Higher
strengths were obtained using portland cement with sodium
silicate and portland cement with fly ash and sodium
silicate. Trade-offs occurred between the costs of the
setting agents and the quality of the product depending on
the agents use'd.for solidification and the dosage applied.
Portland cement proved an excellent setting agent and
yielded excellent physical stability.
Chemical leach tests were conducted to evaluate the
chemical stability of solidified and stabilized samples.
Serial, graded batch Jeach tests were used to develop
desorption isotherms.38 Coefficients for contaminant re-
lease were determined from desorption isotherms for
comparison to those obtained from untreated sediments.
37
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Cadmium and zincwere completely immobilized by some
processes. Proprietary processes were among the best.
Fly ash with lime in some cases increased concentrations
of leachabte contaminants. Solidification/stabilization did
not significantly alterthe sorption capacity of the sediment
for organic carbon. Data were not available to evaluate
the potential of solidification/stabilization technology to
reduce the leachability of specific organic compounds.37
puffalo River. A bench scale solidification/stabilization
study was conducted to evaluate the effectiveness of
solidification/stabilization technologies on the physical
and chemical properties of Buffalo River sediment, New
York. Binders selected for testing included portland
cement, lime/fly ash, and kiln dust. The addition of
activated carbon to the portland cement process was
investigated to determine if it would absorb contaminants
and improve the binding of organics. Physical tests
conducted were the DCS wet/dry and freeze/thaw.
Chemical tests conducted were the TCLP and Standard
Leachate Test (SLT).
Halby Chemical S'rte. Bench-scale treatability studies
were used to evaluate the effectiveness of solidification/
stabilization for binding metals in sediments from Halby
Chemical site in Wilmington, Delaware. Results indicated
that the soilsthemselvesdo not leach appreciable amounts
of metals under TCLP test conditions. Of the two binders
studied (asphalt and cement), asphalt appeared to be the
better binder for reducing leachate concentrations of
arsenic and copper.5
6.6 References
1. USEPA. The Feasibility Study: Development
and Screening of Remedial Action Alternatives.
EPA 9355.3-01 FS3, U.S. Environmental Protec-
tion Agency, 1989.
2. Allen, D.C. and A. J. Ikalainen. Selection and
Evaluation of Treatment Technologies for the
New Bedford Harbor (MA) Superfund Project.
Superfund '88, Proceedings of the 9th National
Conference, 1988. pp 329-334.
3. Male.J.W.andM.J.Cullinane.Jr. Procedurefor
Managing Contaminated Dredged Material.
Journal of Waterway, Port, Coastal, and Ocean
Engineering 114 (5): 545-564,1988.
4. Carpenter, B. PCB Sediment Decontamination -
Technical/Economic Assessment of Selected
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U.S. Environmental Protection Agency, Cincin-
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5. Hokanson, S., R.B. Sukol, S. Giti-Pour, G.
McNelly, and E. Barth. Treatability Studies on
Soil Contaminated with Heavy Metals, Thiocya-
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Semivolatile Organic Compounds. In: Proceed-
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26-28,1990, Washington, D.C. Hazardous Mate-
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6. Dillen, M.R.B. van. Cleaning of Sediments Con-
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for Inland Water Management and Waste Water
Treatment (RIZA), Ministry of Transport and Public
Works, the Netherlands, undated.
7. USEPA. Engineering Bulletin: Solvent Extrac-
tion Treatment. EPA/540/2-90/013, U.S. Envi-
ronmental Protection Agency, Washington, D.C.,
September, 1990.
8. USEPA. Technology Evaluation Report: CF
Systems Organic Extraction System, New
Bedford, Massachusetts. EPA/540/5-90/002, U.S.
Environmental Protection Agency, January, 1990.
9. Sukol, R.B. and G.D. McNelly. Workshop on
Innovative Technologies for Treatment of Con-
taminated Sediments, June 13-14, 1990. EPA/
600-2-900/054, U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1990.
10. Roy F. Weston, Inc. Pilot-Scale Development of
Low Temperature Thermal Degradation and
Solvent Extraction Treatment Technologies for
Explosives Contaminated Waste Water Lagoons.
U.S. Army Toxic and Hazardous Materials
Agency, March, 1985.
11. USEPA. Assessment of International Technolo-
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September, 1988.
12. Schlegel, R. Residues from High Temperature
Rotary Kilns and Their Leachability. In: Forumon
Innovative Hazardous Waste Treatment Tech-
nologies: Domestic and International, Atlanta,
Georgia, June 19-21,1989. EPA/540/2-89/056,
U. S. Environmental Protection Agency, Wash-
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13. Brunner, C.R. Incineration: Today's HotOption
for Waste Disposal. Chemical Engineering, Vol.
94, No. 14, October 12, 1987.
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14. Peacy, J. Special Roundup Feature Report on
Incineration. Pollution Engineering, Vol. 16, No.
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15. USEPA. Mobile Treatment Technologies for
Superfund Wastes. EPA 540/2-86/003(1), U.S.
Environmental Protection Agency, September,
1986.
16. Roy F. Weston, Inc. Incineration Test on Explo-
sives Contaminated Soils at Savannah Army
Depot, Savannah, Illinois. DRXTH-TE-CR-84277,
U.S. Army Toxic and Hazardous Materials
Agency, April, 1984.
17. Nusbaumer, M. and E. Beitinger. Recycling of
Contaminated River and Lake Sediments Dem-
onstrated by the Example of Neckar Sludge. In:
Forum on Innovative Hazardous Waste Treat-
ment Technologies: Domestic and International,
Atlanta, Georgia, June 19-21,1989. EPA/540/2-
89/056, U. S. Environmental Protection Agency,
Washington, D.C., 1989. pp. 231-240.
18. USEPA. PCS Sediment Decontamination -
Technical/Economic Assessment of Selected
Alternative Treatments. EPA/600/2-86/112, U.S.
Environmental Protection Agency, December,
1986.
19. USEPA. A Compendium of Technologies Used
in the Treatment of Hazardous Wastes. EPA/
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Agency, September, 1987.
20. USEPA. Shirco Infrared Incineration System.
EPA/540/A5-89/010, U.S. Environmental Pro-
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21. USEPA. Superfund Innovative Technology
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U.S. Environmental Protection Agency, 1989.
22. USEPA. The Superfund Innovative Technology
Evaluation Program - Progress and Accomplish-
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1990.
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" EPA/540/2-89/056, U. S. Environmental Protec-
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24. Timmons, D.M., V. Fitzpatrick, and S. Liikala.
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25. Reimus, M.A.H. Feasibility Testing of In Situ
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Battelle, Pacific Northwest Laboratories, Rich-
land, Washington, 1988.
26. Averett, D.E., B.D. Perry, and E.J. Torrey. Re-
view of Removal, Containment, and Treatment
Technologies for Remediation of Contaminated
Sediments in the Great Lakes. Miscellaneous
Paper EL90-25, U.S. Army Corps of Engineers,
Vicksburg, Mississippi, 1990.
27. Galson Research Corporation. Laboratory Treat-
ment Results: KPEG Treatment of New Bedford
Soils. .East Syracuse, New York, 1988.
28. Williams, R.T. and C.A. Myler. Bioremediation
Using Composting. Biocycle 31:78-82, Novem-
ber, 1990.
29. USEPA. Handbook on In Situ Treatment of
Hazardous Waste-Contaminated Soils. EPA/540/
2-90/002, U.S. Environmental Protection Agency,
January, 1990.
30. Bedard, D.L. Bacterial Transformation of Poly-
chlorinated Biphenyls. In: Biotechnology and
Biodegradation, D. Kamely, A. Chakrabarty, and
G.S. Omenn, eds. Advances in Applied Biotech-
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31. Abramowicz, D.A. Aerobic and Anaerobic Biode-
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32. Anid, P.J., L. Nies, J. Han, and T.M. Vogel.
Hudson River Model. In: Research and Develop-
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Progress Report, June 1,1989 - June 31,1990.
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and Development, Schenectady, New York, 1990.
33. USEPA. Stabilization/Solidification of CERCLA
and RGRA Wastes: Physical Tests, Chemical
Testing Procedures, Technology Screening, and
Field Activities. EPA/625/6-89/022, U.S. Envi-
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Engineering Laboratory, Cincinnati, Ohio, 1989.
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34. Jones, L. W. Interference Mechanisms in Waste
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35. Ebasco Services Incorporated. Final Supple-
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East Foundry Cove). Ebasco Services Incorpo-
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36. Myers, T.E. and M. E. Zappi. New Bedford
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Laboratory-Scale Application of Solidification/
Stabilization Technology. EL-88-15, U.S. Army
Corps of Engineers, Vicksburg, Mississippi, 1989.
37. USAGE. Disposal Alternatives for PCS Contami-
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from Serial Batch Extraction Tests of Wastes and
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40
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CHAPTER 7
DISPOSAL
7.1 Introduction
Disposal alternatives for dredged material consist of
unrestricted and restricted options. Most dredged mate-
rials are the product of maintenance dredging; the major-
ity of this material is not contaminated and is thus suitable
for unrestricted disposal. Unrestricted alternatives in-
clude unrestricted open-water disposal ("dumping"),
sanitary landfills, and beneficial uses. Since this docu-
ment is concerned with the remediation of contaminated
sediments, unrestricted options will not be discussed
further. Restricted alternatives suitable for contaminated
sediments include capping, confined disposal facilities,
and hazardous landfills.
Pre-testing is essential in deciding on a particular re-
stricted alternative and on the proper design of that
alternative. Francingues et al1 present tests that should
be included as part of this decision making stage.
7.2 Capping
The principal concept for reducing long-term environ-
mental effects associated with open water disposal is to
"cap" (cover or encapsulate) the contaminated material
with clean dredged material. Contaminated sediments
can be capped with clean sediments in situ, orthey can be
dredged, moved, and then capped. By keeping contami-
nated sediment in the waterway, stable geochemical and
geohydrologic conditions are maintained in the sediment,
minimizing release of contaminants to surface water,
ground water, and air. Placement of a clean cap or cover
on top of the contaminated sediment sequesters diffusion
and convection of contaminants into the water column
and prevents bioturbation or uptake by aquatic organ-
isms.2 Capping could also be considered for disposal of
residual solids from treatment or pre-treatment proc-
esses.3
Capping should not be considered a more elaborate
version of conventional open-water dumping. Rather,
capping is an engineering procedure and its successful
performance depends on proper design and care during
construction.4 Six parameters have been identified as
central to the design of an open-water disposal site:
currents (velocity and structure), average water depths,
salinity/temperature stratifications, bathymetry (bottom
contours), dispersion and mixing, and navigation and
positioning (location/distance, surface sea state, etc.).5
As shown in Figure 7-1, capping options include level
bottom capping and contained aquatic disposal (CAD).
Level bottom capping projects place the contaminated
sediments on the existing bottom in a discrete mound.
The mound is covered with a cap of clean sediment,
usually in several disposal sequences to ensure ade-
quate coverage. Where the mechanical conditions of the
contaminated sediments and/orbottom conditions (slopes)
require a more positive lateral control during placement,
CAD options may be applied. These include the use of an
existing depression, excavation of a disposal pit, or con-
struction of one or more confining submerged dikes or
berms."
To reduce short term effects on the water column during
placement, hydraulically dredged material may be dis-
charged below the surface using a gravity downpipe or
submerged diffuser. Such equipment not only reduces
effects on the upper water column but also assists in
accurate placement of the contaminated material and the
clean capping material at the disposal site.2
Capping techniques may not be suitable for the most
highly contaminated sediments. They may be favorable
in some applications because of ease of implementation,
lack of upland requirements, comparatively low cost, and
highly effective contaminant containment efficiency. The
principal disadvantages for open water disposal options
are the concern for long term stability and effectiveness of
the cap and the complications that may occur if remedia-
tion of the disposal site should be required in the future.2
Capped sites will also require monitoring and mainte-
nance to ensure site integrity.4 Additional references for
planning and designing capping operations include Truitt6'7
and Palermo.8
41
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Capping has been used as a disposal technology in Long
Island Sound, the New York Bight, and Puget Sound, in
the U.S.; in Rotterdam Harbor, in the Netherlands; and in
Hiroshima Bay, in Japan. No problems have been re-
ported at capped sites in Puget Sound, one of which is six
years old. The Puget Sound capped sites include sedi-
ments capped in situ and sediments dredged and then
capped.3
7.3 Confined Disposal Facility (CDF)
CDFs are engineered structures enclosed by dikes and
desig ned to retain dredged material. They may be located
upland (above the water table), partially in the water near
shore, or completely surrounded by water. A CDF may
have a large cell for material disposal, and adjoining cells
for retention and decantation of turbid, supernatant water.
A variety of linings have been used to prevent seepage
through the dike walls. The most effective are clay or
bentonik-cement slurries, but sand, soil, and sediment
linings have also been used.
Location and design are two important CDF considera-
tions. Terms to consider in the location of a CDF are the
physical aspects (size, proximity to a navigable water-
way), the design/construction (geology, hydrology), and
the environment (current use of area, environmental
value, environmental effects). The primary goal of CDF
design is minimization of contaminant loss. Accordingly,
potential contaminant pathways must be identified and
controls and structures selected to limit leakage via these
pathways. Contaminants are potentially lost via leachate
through the bottom of the CDF, seepage through the CDF
dikes, volatilization to the air, and uptake by plants and
animals living or feeding in the CDF. Caps are the most
effective way to minimize contaminant loss from CDFs,
but selection of proper liner material is also an important
control in CDFs. Finally, CDFs require continuous moni-
toring to ensure structural integrity.9'10-11
7.4 Landfills
Offsite landfills may be considered for highly contami-
nated material or for treated residuals. There are two
types of landfills: sanitary and hazardous. Highly con-
taminated sediments or sediment wastes may be inap-
propriate for sanitary landfills and must be disposed of in
hazardous landfills, which will add greatly to total treat-
ment cost. Hazardous landfills must be designed to meet
regulatory criteria and must have appropriate state and/or
federal permits. ;
Because dredging often results in large quantities of
dredged material with high water contents, dredging may
not be compatible with landfill disposal. Large quantities
of dredged material and high water content both increase
the volume of material the landfill must accommodate and
thus drive up costs. If use of a landfill is required, then
specific pre-treatment options (such as dewaterihg) and/
or treatment options may have to be considered.
7.5 References
1. Francingues, N.R., M.R. Palermo, C.R. Lee, and
R.K. Peddicord. Management Strategy for Dis-
posal of Dredged Material: Contaminant Testing
and Controls. Miscellaneous Paper D-85-1,
USAGE Waterways Experiment Station,
Vicksburg, Mississippi, 1985.
2. Averett, D.E., B.D. Perry, and E.J. Torrey. Re-
view of Removal, Containment and Treatment
Technologies for Remediation of Contaminated
Sediments in the Great Lakes. Miscellaneous
Paper EL90-25, U.S. Army Corps of Engineers,
Vicksburg, Mississippi, 1990.
Fairweather, V. The Dredging Dilemma.
Engineering, August, 1990, pp. 40-43.
Civil
Palermo, M.R. et al. Evaluation of Dredged Ma-
terial Disposal Alternatives for U.S. Navy
Homeport at Everett, Washington. EL-89-1, U.S.
Army Corps of Engineers, Vicksburg, Missis-
sippi, January, 1989.
Cullinane, M.J., Jr., D.E. Averett, R.A. Shafer,
J.W. Male, C.L. Truitt, and M.R. Bradbury. Alter-
natives for Control/Treatment of Contaminated
Dredged Material. In: Contaminated Marine
Sediments—Assessment and Remediation,
National Academy Press, Washington, D.C.,
1989. pp. 221-238.
Truitt, C.L. Engineering Considerations for
Capping Subaqueous Dredged Material Depos-
its—Background and Preliminary Planning:
Environmental Effects of Dredging, Technical
Notes. EEDP-09-1, U.S. Army Engineer Water-
ways Experiment Station, Vicksburg, Mississippi,
1987.
Truitt, C.L. Engineering Considerations for
Capping Subaqueous Dredged Material Depos-
its—Design Concepts and Placement Tech-
niques: Environmental Effects of Dredging, Tech-
nical Notes. EEDP-09-1, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, Mis-
sissippi, 1987.
43
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8. Palermo, M.R. Design Requirements for Cap-
ping, Environmental Effects of Dredging, Techni-
cal Notes. In preparation, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, Mis-
sissippi, 1991.
9. Cullinane, M.J., D.E. Averett, R.A. Schafer, J.W.
Male, C.L. Truitt, M.R. Bradbury. Guidelines for
Selecting Control and Treatment Options for
Contaminated Dredged Material Requiring Re-
strictions. Final Report, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, Mis-
sissippi, September, 1986.
10. Sukol, R.B. and G.D. McNelly. Workshop on
Innovative Technologies for Treatment of Con-
taminated Sediments, June 13-14,1990. EPA/
600/2-900/054. U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1990.
11. Miller, J.A. Confined Disposal Facilities on the
Great Lakes. U.S. Army Corps of Engineers,
Chicago, Illinois, February, 1990.
&U.S. GOVERNMENT HUNTING OFFICE: MM - 5M40I/M2U
44
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