EPA 905-B-96-003
AUGUST, 1996
DESIGN, PERFORMANCE, AND MONITORING
OF DREDGED MATERIAL
CONFINED DISPOSAL FACILITIES IN REGION 5
Guidance Document
by
Gregory N. Richardson, Ph.D., P.E.
G.N. Richardson & Associates
Raleigh, NC 97603
Ronald C. Chaney, Ph.D., P.E.
Humboldt State University
Arcata, CA 95521
Kenneth R. Demars, Ph.D, P.E.
University of Connecticut
Storrs, CT 06269
Contract 68-CO-0068-43
PROJECT MANAGER
David M. Petrovski
Region V
U.S. Environmental Protection Agency
Chicago, IL 60604
In Cooperation with
Risk Reduction Engineering Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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DISCLAIMER
The preparation of this document was funded by the United States Environmental
Protection Agency (U.S. EPA) under contract No. 68-CO-0068-43. This guidance
is intended to assist individuals desiring information on the design,
performance and monitoring of disposal facilities for contaminated sediments.
Mention of trade names or commercial products does not constitute endorsement
or recommendation of use by U.S. EPA.
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ABSTRACT
This guidance document provides design and performance criteria for Confined Disposal
Facilities (CDFs) used for long-term containment of dredged materials. Sediment remediation
and the implementation of navigational dredging projects require disposal options for dredged
materials which are legally permittable, environmentally acceptable, and economically feasible.
Contaminated sediments represent a high priority environmental problem, especially in the
Great Lakes area. This guidance document presents the regulatory background that influences
the dredging and long-term disposal of dredged materials, as well as design and monitoring
criteria for CDFs consistent with applicable Federal Regulations, and reflective of the
significance and severity of dredged material contamination levels.
Design guidelines are presented in this document that will lead to CDF's providing adequate
environmental performance/protection (referred to in this document as AEPP) to the ecosystem
adjacent to this CDF. AEPP criteria are developed based on an evaluation of potential
contaminant pathways and the impact of such releases on the immediate environment. The
fundamental design philosophy used in developing this document was control of contaminant
pathways using barriers that are technically and economically feasible for the significant
quantities of contaminated dredged sediments that must be safely disposed. Such barriers
may, by necessity, generally differ from those commonly used to contain smaller quantities of
more highly contaminated materials.
Information within the technical documents is organized as follows:
Section 1 Provides a general overview of contaminated dredged material
types, CDF types, and applicable regulations;
Section 2 Reviews the draft EPA/COE dredged material management
strategy and develops AEPP criteria for the CDF types;
Section 3 Provides background on dredged material production and
sediment remedial activities within Region 5;
Section 4 Reviews the design and performance of existing CDFs and
EPA/State remediation projects within Region 5;
Section 5 Defines pathways that allow release of contaminants from CDFs;
Section 6 Provided design recommendations and examples for CDF
containment basins;
in
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Section 7 Provides design recommendations and examples for CDF final
closures; and
Section 8 Defines operational and monitoring requirements for the post-
closure monitoring period.
Appendices are included in this document to provide significant detail on available dredged
material remediation technologies, environmental performance requirements, existing Region 5
CDFs, and the use of geosynthetics in sediment containment systems.
IV
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TABLE OF CONTENTS
Page No.
Disclaimer \\
Abstract jjj
Table of Contents jv
List of Figures vi
List of Tables vi
Acronyms vii
1.0 Introduction 1
1.1 Regulation of Dredged Material Disposal Activities 7
1.1.1 CWA-USACE 404 Program 8
1.1.2 CWA-EPA 404 Program Review 8
1.1.3 CWA-State 401 Program Review 9
1.1.4 CWA-State 402 Program Review 9
1.1.5 Marine Protection Research and Sanctuaries Act (MPRSA) 9
1.1.6 National Environmental Policy Act (NEPA) 10
1.2 Contaminated Sediments 10
1.2.1 Regulation of Contaminated Dredged Materials 10
1.2.2 Presuptive Remediation of Contaminated Sediments 15
1.3 Confined Disposal of Problematic Dredged Materials 15
1.4 CDF Contaminant Pathways 17
2.0 Development of Environmental Performance Criteria For CDFs 18
2.1 Joint USACE/EPA Sediment Management Strategy 20
2.2 Evaluation of Contaminant Pathways 22
2.2.1 Effluent Discharge Quality 26
2.2.2 Surface Water Run-off Quality 30
2.2.3 Plant Uptake 31
2.2.4 Animal Uptake 33
2.2.5 Groundwater Leachate Quality 35
2.2.6 Water Column Discharge Quality 36
2.2.7 Airborne Loss of Contaminant 38
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2.3 AEPP Evaluation Criteria for CDFs 38
2.3.1 Effluent AEPP Criteria 39
2.3.2 Surface Water Run-Off AEPP Criteria 40
2.3.3 Plant Uptake AEPP Criteria 40
2.3.4 Animal Uptake AEPP Criteria 41
2.3.5 Groundwater Leachate AEPP Criteria 41
2.3.6 Airborne Loss AEPP Criteria 42
3.0 Dredged Material Production and Disposal in the Great Lakes 45
3.1 Navigation Dredging by the USAGE 45
3.1.1 In-Lake CDFs 49
3.1.2 Upland CDFs 49
3.2 Sediment Remedial Actions By EPA and States 50
4.0 Design and Performance of Existing CDFs 52
4.1 USAGE (EPA Region 5) Projects 52
4.1.1 CDF Design Criteria/Objectives 52
4.1.2 Example In-Lake CDFs 54
4.1.3 Examples of Upland CDFs 63
4.2 EPA/State Remediation Projects 69
4.2.1 Sediment Remediation Criteria/Objectives 69
4.2.2 Example Remediation Projects 70
5.0 Contaminant Pathway Control 74
5.1 Water Borne Contaminants 74
5.1.1 Effluent Flow Through Weirs and Filters 78
5.1.2 Dike Seepage 84
5.1.3 Foundation Seepage of Leachates 86
5.1.4 Run-Off Contaminant 88
5.2 Contaminant Pathway to Plant and Animal Communities 88
5.2.1 Contaminant Uptake by Plants 91
5.2.2 Contaminant Uptake by Animals 95
5.3 Airborne Emissions Control 97
VI
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6.0 CDF Basin Design Recommendations 99
6.1 Effluent Discharge Through the Dikes 99
6.1.1 Dike Barrier Systems 102
6.1.2 Design Considerations for Dike Barrier Systems 106
6.2 Leachate Discharge to the Groundwater 108
6.3 Impoundment Basin Design Guide 112
7.0 Closure Practices and Design Recommendations 114
7.1 USAGE Closure Objectives 114
7.2 EPA Closure Objectives 116
7.2.1 RCRA Subtitle C Hazardous Waste Landfills 116
7.2.2 RCRA Subtitle D Non-Hazardous Waste Landfills 119
7.2.3 Additional Regulatory Closure Criteria 119
7.3 Design of Closure Components 121
7.3.1 Barrier Layer Design 121
7.3.2 Erosion control Layer Design 126
7.3.3 Airborne Emissions Control Design 128
7.3.4 Plant and Animal Uptake Control Design 129
7.4 CDF Cover Selection Guide 1 30
8.0 Operational and Post-Closure Monitoring 1 33
8.1 Monitoring During Operations 133
8.1.1 Effluent Quality 134
8.1.2 Leachate Discharge Monitoring 134
8.2 Post-Closure Monitoring 135
8.2.1 Surface Water Run-Off Monitoring 135
8.2.2 Plant Uptake Monitoring 135
8.2.3 Animal Uptake Monitoring 135
8.2.4 Volatilization Monitoring 137
References 138
VII
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Appendixes
A. Treatment of Contaminated Sediments
B. Environmental Performance Requirements
B.1 Water Borne Pathways
B.2 Plant Uptake
B.3 Animal Uptake
C. Geosynthetics in Waste Containment Systems
C.1 Barrier Systems
C.2 Drainage/Collection Systems
C.3 Filter Systems
D. CDF-Region 5 Summary Tables
E. RCRA-C Hazardous Waste Landfill Performance Criteria
LIST of TABLES
Table 1.1 Historical Sources of Sediment Contaminants
1.2 CDF Design Criteria Based on Contaminant Level and Partitioning
2.1 EPA Guideline Values for Harbor Sediment Classification
2.2 Sources of Existing Sediment Contamination Information
2.3 Sources and Pathways of Toxic Trace Elements to Plants
2.4 Sources and Pathways of Toxic Trace Elements to Animals
2.5 Evaluation Criteria for Contaminant Pathways
2.6 Maximum Contaminant Levels (MCLs) - SDWA
3.1 Summary Data for Confined Disposal Facilities, U.S. Great Lakes
5.1 Summary of Contaminant Uptake Relationships for Plants and
Animals
5.2 Typical Plant Uptake Factors for Chemicals in Soils and Sludge
5.3 Typical Chemical Bioconcentration Factors in Animals
6.1 Dike Barrier Systems Application in CDFs
7.1 Summary of Closed CDFs in Great Lakes
VIII
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LIST of FIGURES
Figure 1.1 Upland, Shoreline, and Island CDF
1.2 Conceptual Diagram of a CDF
1.3 Contaminant Pathways for Upland CDFs
2.1 Flow Chart Illustrating Framework for Determining Environmental
Acceptability of Dredged Material Disposal Alternatives
2.2 Flow Chart Illustrating Framework for Testing and Evaluation
For Confined (Diked) Disposal
2.3 Elutriate Test
2.4 Modified Elutriate Test Procedure
2.5 Effluent Quality Predictive Technique
2.6 Surface Runoff Evaluation System
2.7 Plant Bioassay Procedure
2.8 Earthworm Bioassay Procedure
2.9 Soil Press for Sediment Leachate Sampling
2.10 Water Column Reactor Unit
2.11 Tiered Gas Emmission Model (RCRA-D)
3.1 Locations of Confined Disposal Facilities, U.S. Great Lakes
4.1 Dike Disposal Areas for Harbor Dredging - Buffalo, New York
4.2 Typical Dike Section - Buffalo, New York
4.3 Bayport Confined Disposal Area - Green Bay Harbor, Wisconsin
4.4 Typical Dike Section - Green Bay Harbor, Wisconsin
4.5 Effluent Filter and Outlet Structure - Green Bay Harbor
4.6 Site Plan of Chicago Confined Disposal Facility
4.7 Typical Dike Section - Chicago CDF
4.8 Site Plan of Lake St. Clair Disposal Area - Dickinson Island,
Michigan
4.9 Weir Structure - Dickinson Island, Michigan
4.10 Siteplan of Sebewaing Disposal Area
4.11 Typical Dike Sections - Sebewaing Disposal Area
4.12 A. Site Location OMC/Waukegan Harbor Superfund Site
B. Siteplan of OMC/Waukegan Harbor Superfund Site
5.1 Transport Mechanisms of Contaminants to Environment
5.2 USAGE Design Procedure for Determining the Design Surface Area
for Sedimentation to Meet Effluent Suspended Solid Requirements
5.3 USAGE Design Procedure for Determining Residence Time (T)
Required for Sedimentation to Meet Effluent Suspended Solid
Requirements
5.4 Control of Contaminant Pathway Through Weir
5.5 Flow Diagram of Alternative Courses of Action to Evaluate Effect
of Sedimentation Disposal Area Effluents
ix
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5.6 Pervious Dikes Filter Systems
5.7 Downflow and Upflow Weirs and Cartridges
5.8 Weir Design Nomograph
5.9 Seepage of Effluent Through Dike
5.10 Control of Foundation Leachate Generation
5.11 Surface Water Run-off Mechanisms Related to Precipitation on CDF
5.12 Food Web Drawing Showing General Flow of Nutrients and Metals
5.13 Mechanisms Involved in Plant Uptake of Contaminants in Capped
and Un-Capped CDFs
6.1 Dike Effluent Discharge Control
6.2 Alternative Dike Section Barriers
A. Chicago CDF Dike Section
B. Grout Filled Fabric Form Barrier
C. Clean Sand Effluent Barrier
6.3 A. Buffalo CDF Dike Section
B. Clogged Filter Fabric Barrier
6.4 Summary of Permeability Data for Toledo Dredgings
6.5 Leachate Discharge Control
6.6 Impoundment Basin Design Guide
7.1 Cover Related Containment Pathway Control
7.2 EPA RCRA Final Cover Guidance
A. RCRA Minimum Technology Guidance Cover
B. RCRA Minimum Technology Guidance Cover with
Supplemental Layers
7.3 EPA CERCLA Landfill Cover Selection Guide
7.4 DOE Water-Balanced Cover
7.5 Soil Barrier Performance
A. Strain vs. Differential Settlement
B. Ultimate Strain vs. Plasticity for Clays
7.6 CDF Cover Selection Guide
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ACRONYMS
AEPP Adequate Environmental Performance and Protection
ARAR Applicable or Relevant and Appropriate Regulation
ARCS Assessment and Remediation of Contaminated Sediments
ASTM American Society for Testing and Materials
AVS Acid Volatile Sulfide
CAA Clean Air Act
CAD Contained Aquatic Disposal
CDF Confined Disposal Facility
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CSO Combined Sewer Overflow
CWA Clean Water Act
DOE United States Department of Energy
EEC European Economic Commission
EIS Environmental Impact Statement
EP Extraction Process
EPA Environmental Protection Agency
EqP Equilibrium Partitioning
FDA U.S. Food and Drug Administration
FIFRA Federal Insecticide, Fungicide, and Rodenticide Act
GAO General Accounting Office
GLNPO Great Lakes National Program Office
GLWQA Great Lakes Water Quality Agreement
HSWA Hazardous and Solid Waste Amendments (1984)
MCL Maximum Concentration Level
MPRSA Marine Protection, Research, and Sanctuaries Act
MSW Municipal Solid Waste
MTG Minimum Technology Guidance
NEP National Estuary Program
NEPA National Environmental Policy Act
NETAC National Effluent Toxicity Assessment Center
NMOC Non-Methane Organic Compounds
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
PRP Potentially Responsible Party
RCRA Resource Conversation and Recovery Act
XI
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RHA Rivers and Harbors Act
SARA Superfund Amendments and Reauthorization Act
SDWA Safe Drinking Water Act
SLT Standard Leachate Test
SQC Sediment Quality Criteria
TBP Theoretical Bioaccumulation Potential
TCLP Toxicity Characteristic Leaching Procedure
TIE Toxicity Identification Evaluation
TSCA Toxic Substances Control Act
TSS Total Suspended Solids
USAGE United States Army Corps of Engineers
USFWS United States Fish and Wildlife Service
VOC Volatile Organic Compound
WQS Water Quality Standards
MISC\GUIDANCE.INI
XII
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SECTION 1
INTRODUCTION
Throughout the Great Lakes, about four million cubic yards of sediments are dredged annually to
maintain navigation in channels and harbors for commercial, military and recreational users, and as
part of environmental projects (EPA, 1990). Sediment is the material that settles to the bottom of a
body of water and is primarily composed of soil particles consisting of clays, silts, and sands,
organic matter, shells, and can include varying quantities of residuals from industrial discharges
polluted by synthetic organic compounds and heavy metals. Many of the waterways are adjacent to
urban and industrial areas and the sediments in these areas are often contaminated from various
adjacent sources. A listing of industries associated with particular sediment contaminants is
presented on Table 1-1. Such contamination is typically historical and much of it predates
regulatory control. Additionally, ongoing releases from combined sewer overflows (CSOs) can be
locally significant. Sediments are also contaminated by non-point sources such as agricultural run
off. A portion of the sediments are so highly contaminated that they require remedial action. About
one-half of the total amount of sediments dredged (approximately 2 million cubic yards) are
sufficiently contaminated to preclude their unconfined release to the environment. In this document,
such materials are referred to as problematic sediments. The disposal of these dredged materials in,
and technical guidance for the design of confined disposal facilities (CDFs) is the focus of this
document. These contaminated sediments require special consideration during dredging and
disposal operations because of potentially adverse impacts on water and air quality and aquatic
organisms. Sound planning and design of dredging operations and disposal facilities are necessary
to protect the environment, while keeping these activities economically viable. The remaining half of
the sediments are generally classified as clean and suitable for unconfined disposal.
The regulatory requirements for the disposal of dredged material are determined by both the type
and level of the contaminants associated with the dredged material, as well as the extent to which
the contaminants could potentially be released from the sediments to proximal air, ground water or
surface water. To date, regulatory concern with most contaminated dredged material disposal
projects have been focused primarily on containment of release routes to water, but as decisions
need to be made on the proper handling of some of the more contaminated materials remaining in
the region, potential contaminant loss pathways like air emission and seepage of free oil-phase
organic contamination are being examined more closely. This is reflected in Table 1.2, which
depicts several pertinent relationships between the level of sediment contamination, the degree of
contaminant partitioning to the water associated with the sediments, in conjunction with three
conceptual categories under which sediment disposal can occur and the significant disposal
regulations. As depicted on Table 1.2, these three conceptual approaches to dredged material
disposal are labeled "beneficial use or open water disposal," "solids retention" and "hydraulic
isolation."
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ro
dEPA REGION s
CONTAMINANTS
Acenaptithene
AUrin
Ammonia
Anllne
Arsenic
Benzo(a)anthracane
Benzo(a)pyrene
Cadmium"
Chbrdane
Chbrpyrilos
Chromium
Copper
Cyanide'
T5DT
DDT
DieUrin
Endrin
Ethyl Paralhlon
Fluoranthene
Heotachtof
HCB
:BD
HCCPD
Lead
Mercury
Table 1.1
Historical Sources of Sediment Contaminants
2-Methytnaphthalena
Nickel
Ol and Grease
PCBs
Phenarthrene
Phosphorus
Pyrene
Selenium
TCDD
TCDF
Toxaphene
Zinc
i
li
f
I
1
Noveiitwr 25, 1992
REF RENCES: nil, edition Merck Index A Overview ol Sedmenl Dually In U.S.. Juno 1987; Prtndptes of Walef dually Management I960; sources ol poMon In Wisconsin Storm Wale,
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Table 1.2 CDF Design Criteria Based on Contaminant Level and Partitioning Potential
CO
Uncontaminated Highly Contaminated
Sed
ments Sediments
CWA 404 Partitionong > State WQS Significant
Gui
Minor Sediment
Contamination
Minimal
Partitioning
Beneficial Use or
Open Water
Disposal
Passes 404
Evaluation for
Open Water
Disposal
CWA 401
Certification for
Dredged Material
Discharge
^L
dance or not Meetir
ig CWA 404 Partil
ioning
PROBLEMATIC SEDIMENTS
Minor Partitioning
Solids Retention
Approach
Increasing Degree of Sediment
Isolation
Filter Intake CDFs
CWA 401 Certification for Discharge
Moderate Partitioning
Hybrid Approach
Hydraulic Isolation
During Sediment
Disposal Only
CWA 401 Certification
for Point or Diffuse
Discharge
Extensive
Partitioning
Hydraulic Isolation
Approach
Increasing Degree
of Hydraulic
Isolation
CWA 401
Certification for
Point Discharge
4. 07 1 IQAPF PHP DF^IfiM MAMI IAI _t
4- 9HORFI INF AND 1
N-LAKE CDF DESIGNS -
.A
RCRA^SCA
Sediments
Hydraulic Isolation CDF
MTG Design
(Appendix E)
CWA 401 Certification for
Point Discharge
CWA 402 Permit for a
Point Discharge
TSCA "Third Alternative"
Design, 40 CFR
761.60(a)(5)
Conformance with
Technology Guidance
4_ i ipi AND PHF DESIGNS -*
4 REGION 5 PDF GUIDANCE DF^IGN5! -*
P\A/A ccr^TinM AF\A AMR CDA/I iCAr-e CDAMCVA/nok" _&
INCREASING DEGREE OF SEDIMENT CONTAMINATION
»JL---. -*
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The Clean Water Act (CWA) governs the discharge of dredged material into "waters of the United
States." If the level of sediment contamination is sufficiently low so that the unconfined release of
the sediments into the environment would not have an unacceptably adverse environmental impact
and would not result in an exceedance of the applicable State Water Quality Standards (WQS), after
consideration of mixing, the sediments could be disposed of at an approved open water disposal
site or placed in the environment in an unrestricted manner. An example of such unrestricted or
unconfined placement would be the use of dredged material for beach nourishment. As shown on
Table 1.2, no discharge of dredged material into US waters is permitted under CWA Section 404 if it
causes violations of any applicable State WQS. Therefore State WQS certification under CWA
Section 401 is required in order for a dredged material discharge permit to be issued. As discussed
further in Section 1.1.3, the State may opt to deny, waive, certify, or certify with conditions which
may be similar to CWA Section 402 NPDES permit conditions. Dredged materials which can not
meet the CWA standards for open water disposal or beneficial use, i.e. problematic dredged
materials, must be segregated from the environment to some extent. Sediments which cannot be
released to the environment in an unrestrictive manner are labeled problematic dredged material in
Table 1.2. The disposal of problematic dredged materials is the focus of this document.
UPUflO
(adapted from USACE/EPA, 1992)
Figure 1.1 Upland, Shoreline, and Island CDF
The USAGE uses confined disposal facilities (CDFs) to contain contaminated sediments which
cannot be released without control to the environment and to facilitate settling and disposal of clean
sediments at upland sites. As shown on Figure 1.1, CDFs can be located at both upland and in-lake
sites. CDF designs reflect the level of isolation which the sediments under consideration warrant.
As diagramed on Table 1.2 and as discussed below, CDF designs can be grouped under two
headings; CDFs which physically isolated the sediment solids from the adjacent environment (solids
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retention) and CDFs which hydraulically isolate the sediments and any derived effluent from the
adjacent environment (hydraulic isolation).
Dredged materials typically contain large amounts of water. Depending upon the method used to
excavate the materials, dredged materials are typically composed of 50 to 95 % water by weight.
The disposal of large quantities of material with a high percentages of both solids and water
presents both technical and regulatory challenges unique to dredged materials. Generally, the
disposal of wastes which have a high percentage of water is regulated by the CWA while the
disposal of waste high in solids is regulated under RCRA. Given the large quantities of water and
solids, CDFs commonly incorporate considerations from both regulatory program requirements into
their design.
Commonly under the CWA, aqueous wastes are sent through one or more treatment steps. Each
treatment step targets a contaminant or group of contaminants with similar chemical or physical
properties. Once the concentration of contaminants has been reduced sufficiently to comply with
applicable standards, the treated effluent is generally released to the environment as a point source
discharge under Section 402 of the CWA or as a dredged material discharge under CWA Section
401. Often dredged material discharges and CDF return waters are sufficiently dilute as to require
little or no treatment in order to comply with State WQS after a mixing zone is applied. In contrast,
solid wastes under RCRA are disposed of in facilities designed to hydraulically isolate the wastes
and derived liquids from the ambient environment. Precipitation, groundwater, or surface waters that
breach the facility and come in contact with the waste are termed leachate. RCRA facilities include
systems to collect and remove leachate from within the facility to isolate it from the proximal
environment. After collection, the leachate is removed from the facility for treatment and disposal.
Additionally, bcth TSCA and RCRA disposal facilities are prohibited from receiving wastes having
free liquids.
Most contaminants are tightly bound (sorbed) to the solids which compose the sediments.
Consequently, a principal criterion for CDF designs has been the retention of as high a percentage
of the dredged material solids as practical. CDFs which retain the contaminated dredged material
also retain and isolate most of the contamination from the environment. CDF designs premised
upon this approach are included under the portion of Table 1.2 labeled "solids retention." Increasing
levels of contaminant concentrations would be reflected in CDFs with an increasing degree of
sediment isolation. This is generally reflected in more elaborate CDF designs aimed at the removal
of lower concentrations of suspended solids from the water entrained with the sediments during the
dredging process. In the absence of significant partitioning of contaminants to the associated free
water phase, and given the removal and retention by the CDF of the sediment solids, this approach
has been environmentally acceptable.
CDFs can also be designed to include aspects of both the solids retention approach and the
hydraulic isolation approach. These are exhibited during different periods of the life of the facility.
As depicted on Table 1.2, such composite CDF designs are termed "hybrid" in this document. An
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example of a hybrid facility is provided by the Chicago CDF, which is further described in Section
4.1.2. This facility was designed to hydraulically isolate the CDF interior from the adjacent waters
during placement of sediments within the CDF. Hydraulic isolation during disposal is accomplished
by pumping water from the interior of the CDF at a rate which is greater than or equal to the rate of
disposal of dredged materials and associated waters. This eliminates or greatly reduces the
increase in head that would normally accompany the filling of the CDF. The water removed from the
CDF is treated and then released to the environment via a point discharge. When placement of
dredged materials is not occurring, the pumping is stopped and the CDF operates under the
conventional solids isolation approach. This allows the physical retention of solids while allowing
the drainage of CDF waters to the surrounding environment.
In contrast, should sediments under consideration be releasing, that is partitioning, contaminants of
concern to the aqueous phase at a concentration(s) of environmental significance, the solids
retention approach may no longer be appropriate. At this point, a CDF design should consider not
only the isolation of the sediment solids themselves, but also any associated water. This could
include the water entrained with the sediments when dredged as well as any ground water, surface
water, or precipitation which found its way into the CDF and came in intimate contact with the
contaminated sediment. Under this scenario, the hydraulic isolation of the sediment, as well as any
effluent from the proximal environment, may be required. CDF designs premised upon this
approach to sediment disposal are included in Table 1.2 under the heading of "hydraulic isolation".
As indicated on Table 1.2, the degree of hydraulic isolation required increases with the increasing
potential of the contaminants to partition to the aqueous phase.
As the environmental significance of the contaminant partitioning increases, CDF designs must
provide a greater degree of hydraulic isolation A worst-case CDF design, providing a high degree of
hydraulic isolation for the dredged materials, is depicted on the right-side of Table 1.2. The design
criteria for this worst-case CDF design is based on RCRA Minimum Technology Guidance (MTG)
for hazardous waste landfills. An explanation of these design criteria is provided in Appendix E.
CDFs conforming with these criteria would perform in a manner similar to RCRA hazardous waste
landfills and TSCA chemical waste landfills. In those instances where the dredged materials are
highly contaminated and the applicable regulations allow for land disposal, a CDF complying with
MTG criteria would provide adequate environmental performance/protection (AEPP) to the
ecosystem adjacent to the facility. As discussed below, such a CDF design may also form the basis
of an acceptable TSCA sediment disposal application under 40 CFR Part 761.60(a)(5) for the
disposal of dredged material contaminated with PCB concentrations equal to or exceeding 50 ppm.
This disposal option for PCB contaminated materials is commonly referred to as "the TSCA third
alternative."
The partitioning of contaminants to the proximal aqueous phase has a temporal component which
the reviewer of a CDF application should be aware of. The release of contaminant to the aqueous
phase during the act of dredging or at the time of placement in the CDF are governed by the short
term chemical kinetics associated with the dredging process. Laboratory procedures, e.g., the
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elutriate and the modified elutriate tests (discussed in Section 2.2.1), used to quantify contaminant
releases to water during these events reflect this. In contrast, the contaminant concentration within
the pore water fluids of dredged materials after disposal would tend to be significantly higher. These
post-disposal pore water contaminant concentrations would be better approximated by long term
equilibrium concentrations that would eventually be established between the contaminants
associated with the sediments and the adjacent aqueous phase. Such higher post-disposal pore
water contaminant concentrations can move advectively through the sediments due to natural
hydraulic gradients. Consequently, the CDF design should reflect these higher post-disposal
partitioning concentrations in the pore water. Without control, such fluids could migrate from the
CDF and impact the proximal environment.
Design guidelines are presented in this document that allow the design of CDFs for problematic
dredged materials to provide AEPP to the ecosystem adjacent to this CDF. AEPP criteria are
developed based on an evaluation of potential contaminant pathways, the nature and concentration
of contaminants associated with the sediments, and the impact of such releases on the immediate
environment and to the ecosystem as a whole. The regulatory and design requirements for CDFs
are influenced by both the level of contaminants within the dredged material and the degree to
which the contaminants partition between the sediment solids and water. These partitioning factors
are discussed in Section 2. Satisfactory design, performance, and monitoring of CDFs requires the
evaluation of all potential pathways and a clear understanding of the partitioning of the contaminant
between the dredged material particles and the impacted waters.
The fundamental design philosophy used in developing this document was control of contaminant
pathways using technically effective barriers that are economically feasible for the significant
quantities of lightly contaminated dredged materials that must be safely disposed.
1.1 Regulation of Dredged Material Disposal Activities
The basic framework for federal water pollution control regulation was established by the Federal
Water Pollution Control Act (FWPCA) established in 1972. In 1977, FWPCA was renamed the
Clean Water Act (CWA) and amended to provide regulatory control of toxic water pollutants.
Sections 401 and 404 of the 1977 amendments to the CWA provide regulatory authority to USAGE,
EPA and the States over dredged material disposal activities. In addition, because permitting under
Section 404 is a major Federal action under the definitions in the regulations (40 CFR 1508.18) for
implementing the National Environmental Policy Act (NEPA), all 404 disposal projects are subject to
full disclosure public review of the project planning process. Under NEPA there is a requirement that
alternatives be examined as well as requirements to disclose project alternative compliance with
other applicable Federal and State environmental laws, including the River and Harbor Act of 1910,
the Clean Air Act, the Watershed Protection and Flood Prevention Act, the Toxic Substance Control
Act (TSCA), the Resources Conservation and Recovery Act (RCRA), the Fish and Wildlife
Coordination Act, the State Historic Preservation Act, the Endangered Species Act, and any
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applicable Federal Executive Orders. TSCA and RCRA may be applicable for disposal of
problematic dredged materials under certain conditions, discussed in Section 1.2.1.
1.1.1 CWA - USAGE 404 Program
Section 404 of the CWA regulates the disposal of dredged or fill material into navigable water by
granting the US Army Corps of Engineers (USAGE) the authority to designate disposal areas and
the authority to control their use. Navigable waters now include all waters which may be susceptible
to use in interstate commerce, or the use, degradation, or destruction of which could affect interstate
commerce. The CWA regulates the impact of effluent discharge and dredge material disposal
activities on navigable waters. As such, the CWA typically addresses the disposal or impact of
materials having a high liquid and low solid content. All states within Region 5 are authorized under
the CWA and have implemented WQSs that are as strict or stricter than those in the CWA, and
these States must certify or waive WQS Certification of all proposed dredged material disposal into
the US waters in order to comply with 404 permit requirements.
In approving a discharge site for a 404 permit, the USAGE applies guidelines developed jointly by
USAGE and EPA in a Memorandum or Agreement (55 FR 9211, March 12, 1990) as codified in 40
CFR Part 230. These guidelines require that dredged or fill material should not be discharged into
an aquatic ecosystem unless it can be demonstrated that the discharge will not have an
unacceptable impact either individually or in combination with other activities that could affect the
ecosystem. A primary emphasis of this review is the ability of the disposal operation to be carried
out to satisfy the four requirements found in Section 230.10. These requirements are as follows:
230-10(a) The discharge site must represent the least damaging, practical alternative; 230.10(b)
Requires compliance with established legal standards (e.g. State Water Quality Certification);
230.10(c) No significant degradation of the aquatic ecosystem; and 230.10(d) All practical means
must be made to minimize or mitigate adverse environmental impact. The concept of a "Mixing
Zone" in the vicinity of the point of discharge is introduced in 404 (b) (1) guidelines presented in 40
CFR 230 and may also appear in State water quality regulations. This concept allows containment
concentrations to exceed State WQS only within a predefined mixing zone that is immediately
adjacent to the point of discharge or dredging activity. The mixing zone analysis is being eliminated
by many States in favor of WQS limits based on biological concentrating contaminants (BCC). BCC
considerations are discussed in Sections 2.2.3 and 2.2.4.
1.1.2 CWA - EPA 404 Program Review
Under CWA 404(c), the EPA Administrator is given authority to veto a Section 404 permit issued by
USAGE if the administrator determines the discharge of dredged or fill materials into the specified
disposal area will have an unacceptable effect on municipal water supplies, shellfish beds, fishery
areas, wildlife, or recreational areas. EPA has promulgated regulations that define the
environmental restrictions associated with these disposal areas [ 40 CFR Part 231 ].
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1.1.3 CWA - State 401 Program Review
As stated above, Section 401 of the CWA provides that an application for a 404 permit must include
a certification from the State in which the discharge originates that the discharge will comply with the
following sections of the CWA:
301-Effluent Limitations
302-Water Quality Related Effluent Limitations
303-Water Quality Standards and Implementation Plan
306-National Standards of Performance
307-Toxic and Pretreatment Effluent Standards.
Primary emphasis in this review is maintenance of State WQS beyond the mixing zone at the point
of discharge. The State must establish procedures for public notice for all applications for 401
Certification. A 404 permit cannot be granted, and a USAGE maintenance project cannot proceed if
certification is denied by the State.
1.1.4 CWA - State 402 Program Review
The continuing discharge of rainwater and/or seepage from a CDF is also subject to control under
the CWA. Such discharges may be required to adhere to discharge limitations, based on State 401
WQS Certification and authority. Some confusion has occurred in the past because regulations
under Section 402, the NPDES program also seem to be appropriate. EPA Region 5 has expressed
interest in using Section 402 to regulate certain types of discharges from CDFs, such as rainwater,
that are not specifically exempted from Section 404. However, Section 402 has never been used for
this purpose, and Section 401 has equivalent power. A State may, when appropriate, issue a 401
Certification letter that could be virtually indistinguishable in content from a typical NPDES permit.
However, because most CDF releases , which are usually diffuse and intermittent, do not usually
violate State WQS outside of an approved mixing zone, State 401 Certifications may range from
simple waiver letters to permit-like letters requiring specific pollution monitoring and limits, ground
water monitoring requirements, fish migration timing restrictions, and even plan modifications that
may or may not be acceptable to the USAGE or the permittee. Any project consisting of problematic
sediments or dredged materials is likely to require considerable effort coordinating for an acceptable
401 Certification from the State.
1.1.5 Marine Protection Research and Sanctuaries Act (MPRSA)
Section 102 of MPRSA requires EPA, in consultation with USAGE, to develop environmental criteria
for all ocean disposal. Section 103 of MPRSA provides that USAGE must specifically authorize all
ocean disposal of dredged materials. Since Region 5 applications do not involve ocean disposal, the
provisions of MPRSA are not applicable to this document.
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1.1.6 National Environmental Policy Act (NEPA)
Dredged material disposal activities must comply with applicable NEPA requirements regarding
identification and evaluation of alternatives associated with the dredging project. Sections 102(2)
and 102(2)(E) of NEPA require the examination of reasonable alternatives to the actions proposed
by the lead Federal agency. All alternatives, even those discarded, must be analyzed in an
Environmental Assessment (EA) or Environmental Impact Statement (EIS). For Federal dredging
projects, the USAGE is responsible under NEPA for developing alternatives for the discharge of
dredged material. The USAGE is also responsible for preparing NEPA documents for Section 404
permit decisions. NEPA does not define performance objectives, but does require the process
evaluation procedure.
1.2 Contaminated Dredged Materials
1.2.1 Regulation of Contaminated Dredged Materials
For the purposes of this document, dredged materials are considered contaminated when the
ambient or teachable concentration of metals or organic compounds exceed Federal RCRA or
TSCA regulatory limits or when contamination exists in high enough concentrations and are
sufficiently available to affect human and/or ecosystem health. Contaminated dredged material may
threaten human health by direct exposure or when contaminated water or organisms are consumed.
Consequently, an acceptable disposal option for such sediments will entail some form of isolation
from the ambient environment. Contaminants in sediments can be from point sources (municipal or
industrial effluent), non-point sources (e.g. agricultural run-off or airborne sources), and from other
sources such as spills or leaks.
RCRA and TSCA regulations provide for the land disposal of contaminated materials in cells that
hydraulically isolate the waste material from proximal ground and surface waters. Wastes placed
within such landfill cells must not contain free liquids as defined by the paint filter test (EPA Method
9095). RCRA and TSCA land disposal regulations are therefore directed at wastes that are very
high in solids and have little or no free liquids. Conversely, CWA regulations, previously discussed
in Section 1.1, are directed at the disposal of waters containing very small concentrations of
suspended solids and partitioned contaminants. With large portions of both water and solids,
environmentally acceptable disposal options for dredged sediments combine aspects common to
both of these regulatory perspectives.
In general, the potential for sediments to hold or bind contaminants increases with increasing
percentages of fine grained sediments (silts and clays) and organics. Fine grained sediments have
a high surface area per unit weight and significant ionic forces that attract and retain many classes
of contaminants. The presence of organic matter increases the affinity of sediments for metals and
organic contaminants.
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Sediment acidity and oxidation/reduction status also affect the mobility and biological availability of
contaminants. Strongly acidic (low pH) sediments slow microbial activity and increase the soluble
level of toxic metals. Weakly acidic to slightly alkaline sediments result in less mobile metals. The
oxidation/reduction potential of a sediment, as measured by the redox potential of the sediment, has
a major effect on the capture or release of metals by a sediment. Frequently, the sediment
contaminants are chemically stable under the geochemical conditions existing within the in-situ
sediments. However, changes in the pH or redox potential of a sediment during dredging or
disposal will substantially affect contaminant mobilization. This influences the partitioning of the
contaminant between the sediment solids and the pore water. EPA is currently updating equilibrium
sediment quality criteria (SQC) that normalize non-ionic organic contaminants to organic carbon and
metal contaminants to acid volatile sulfide (AVS). The role of long term equilibrium contaminant
partitioning is reflected in the regulatory present scheme previously shown on Table 1.2.
Contaminant mobilization mechanisms in dredged materials, SQC, and remediation of contaminated
materials are discussed in greater detail in Appendix A.
Problematic Dredged Material In this document, problematic dredged material are defined as
materials which are sufficiently contaminated to preclude their unconfined release to the
environment, e.g. open water disposal or beneficial reuse. In Region 5, problematic dredged
material are commonly the result of non-point source releases and spills or point-source releases
which occurred prior to the effective date of the CWA as well as most other environmental
regulations. Because the unrestricted release of problematic dredged materials to the environment
is unacceptable, the AEPP disposal criteria for these materials will require containment to some
extent. The extent of containment required is dependent upon the nature, concentration, and
partitioning potential of the specific contaminants. Provided an acceptable level of suspended solids
is achieved in the effluent, the AEPP criteria for the disposal of sediments associated with lew levels
of tightly sorbed contamination may require only physical isolation of the dredged material. AEPP
criteria for the disposal of sediments with higher levels of contaminants that partition to the aqueous
phase at concentrations of concern will generally require hydraulic isolation of the dredged material
as well as any derived effluent. These two approaches to the disposal of dredged materials have
been labeled the "Sediment Retention Approach" and the "Hydraulic Isolation Approach"
respectively. As discussed below, the disposal of sufficiently contaminated problematic dredged
material can be regulated by RCRA-C and/or TSCA. AEPP criteria for the disposal of such highly
contaminated materials which meet the regulatory requirements for land disposal will require a
hydraulic isolation design based on RCRA-C MTG as summarized in Appendix E.
TSCA Dredged Material Enacted in 1976 by Congress in response to the discovery that DDT
and other pesticides were impacting waterfowl and that PCBs were present in large numbers of
birds and fish, TSCA required EPA to test certain existing chemicals to determine if they posed an
unacceptable human health or environmental risk. While the twenty-nine sections of TSCA cover a
wide range of considerations, TSCA has become fundamentally associated with the control of PCBs
at concentrations equal to or greater than 50 ppm. The use, control and disposal of PCBs under
TSCA are covered in 40 CFR Part 761, as issued in 1982. Subpart D specifies that, in general,
11
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PCBs at concentrations equal to or greater than 50 ppm must be disposed of in an incinerator.
However, 40 CFR Part 761.60(a)(2) also allows PCBs at concentrations less than 500 ppm to be
disposed of in a chemical waste landfill as defined in 761.75. TSCA specifically addresses dredged
sediments contaminated with PCB concentrations equal or exceeding 50 ppm in 761.60(a)(5). This
section provides three methods of PCB contaminated sediment or sludge disposal: (1) incineration,
(2) placement in a TSCA chemical waste landfill, and (3) using a disposal method approved by the
Regional Administrator. Application for the "3rd alternative" must demonstrate that disposal in an
incinerator or chemical landfill is not reasonable and appropriate, and that the alternate disposal
method will provide adequate protection to health and the environment. Performance criteria which
could form the basis for the disposal of TSCA regulated sediments are presented in Appendix E.
TSCA also allows for the temporary storage of wastes containing PCBs at concentrations equal to
or greater than 50 ppm for a time period not to exceed 1 year in an approved storage facility.
A chemical waste landfill under 40 CFR Part 761.75 (TSCA) must satisfy well defined technical liner
requirements. These technical liner requirements are based on hydraulic isolation of the PCB
contaminated material and include the following:
(1) As a minimum, the landfill must have 4 feet of in situ natural soils or 3 feet of
compacted soils having a hydraulic conductivity equal to or less than 1 x 10'7 cm/sec.
A synthetic membrane liner must be used when, in the judgement of the Regional
Administrator, the hydrogeologic or geologic conditions at the site require it to
achieve an equivalence to these criteria.
(2) The landfill design must include a leachate collection/monitoring system.
(3) The bottom of the liner system must be at least fifty feet from the historic high water
table. Floodplains, shorelands, and groundwater recharge areas shall be avoided.
(4) The landfill must be protected from the 100 year flood.
(5) The landfill site must have low to moderate relief to minimize long-term erosion.
(6) The landfill must be equipped with a monitoring system that allows both ground and
surface water to be monitored.
These regulatory requirements, while not consistent in minor design details with those required by
RCRA-C for a hazardous waste landfill, are consistent with the full containment concepts of RCRA.
The TSCA chemical landfill requires a greater thickness of vertical buffer between the liner and
seasonal high groundwater table. From a dredged material disposal perspective, the 50 foot above
the historic high water table requirement would virtually eliminate all CDFs for TSCA waste in
Region 5 if not for the 3rd alternative, e.g. disposal method approved by the Regional Administrator.
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The conceptual basis for the TSCA regulations is the hydraulic isolation of the waste from surface
and ground waters. This is identical to the conceptual basis for RCRA-C and RCRA-D regulations.
RCRA Subtitle C Sediments As promulgated in 1976 and amended by Hazardous and Solid
Waste Amendments (HSWA) in 1984, RCRA-C is a national regulatory mechanism that controls the
treatment, storage, and disposal of hazardous waste as defined under 40 CFR 261 and thereby
minimizes the present and future threat to human health and the environment. 40 CFR 261
specifies that a waste is hazardous if it is not excluded from regulation as a hazardous waste and it
meets any of the following criteria: 1) is named as a hazardous waste and is included in one of
three lists under 261, 2) exhibits a hazardous waste characteristic, 3) results from the mixture of a
waste with listed hazardous waste, 4) is derived from a listed hazardous waste or exhibits a
hazardous waste characteristic, and 5) is an environmental media which contains a listed hazardous
waste. The first list under 261 contains hazardous wastes from nonspecific sources (e.g. spent
halogenated solvents, such as toluene). The second list identifies hazardous wastes which
commonly result from manufacturing or industrial processes (e.g. bottom sediment sludge from the
treatment of waste water by wood preservers). The third list contains commercial chemical products
or chemical manufacturing intermediates which, when discarded, must be treated as hazardous
waste. If a waste is not listed as hazardous, it is still covered by RCRA if it exhibits one of four
hazardous waste characteristics: ignitability, corrosivity, reactivity, or toxicity. For example, under
the definition provided for toxicity, a solid waste is hazardous if the extract obtained from the sample
using the Toxic Characteristic Leaching Procedure (TCLP) test contains a hazardous constituent at
or above the regulatory threshold provided for that constituent. To date, most RCRA-C sediment
characterization efforts in Region 5 have focused on toxicity as defined by the TCLP test.
Of major potential significance to the disposal of contaminated dredged materials is the land
disposal ban enacted by HSWA. These regulatory requirements mandate that hazardous wastes or
Subtitle C media must be properly and adequately treated prior to land disposal. Such treatment
would include destruction of organic constituents and/or solidification of the metal constituents in the
waste such that it will pass a TCLP test. In 1986, EPA banned the land disposal of untreated
hazardous wastes containing dioxin and solvents. Next, in 1987, EPA banned the disposal of
certain untreated hazardous wastes that had previously been banned by California. Third, EPA
published a ranking of all other hazardous wastes based on their hazard or volume. From 1988 to
1990 EPA enacted a ban on the land disposal of these wastes without treatment. By banning the
direct land disposal of such hazardous wastes, Congress sought to reduce the rate of hazardous
waste production and the long term risks associated with hazardous waste disposal.
The treatment requirements under RCRA-C for contaminated environmental media such as
sediment, depend upon the type of RCRA-C contaminant associated with the sediment.
Conceptually, sediments can be contaminated with one or more listed hazardous waste or can
exhibit one or more hazardous waste characteristics. In practice however, the identification of
sediments which require compliance with the RCRA-C regulations for listed waste has been rare.
This is due to the RCRA-C exclusions under 40 CFR 261.4(a) for hazardous waste mixed with
13
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domestic sewage and waste released from industrial point source discharges subject to Section 402
of the CWA. An overview of the treatment and disposal regulations for sediments requiring
compliance with RCRA-C is provided below.
The treatment and disposal of sediments contaminated with a listed hazardous waste can be
handled in one of two ways. Where feasible, such sediments can be treated to the extent that the
sediments no longer "contain" the listed waste. The threshold levels for this determination are
provided by the EPA Region in which the activities occur. Treatment procedures which reduce the
listed RCRA-C wastes from the sediment to concentrations below these thresholds render the
sediments nonhazardous. Subsequent disposal of the sediments is then not regulated under RCRA-
C. In contrast, if the treated sediments still contain listed hazardous wastes, but meet the treatment
standards provided under 40 CFR 268, the disposal of the sediments would continue to be
regulated under RCRA-C. Consequently, such treated sediments would need to be dewatered until
the sediments pass the paint filter test and subsequently placed in a RCRA-C disposal facility. A
similiar treatment scenario exists for sediments that exhibit a RCRA-C hazardous waste
characteristic.
Similarly, the treatment requirements for dredged sediments which exhibit a RCRA-C hazardous
waste characteristic can also be addressed through one of two scenarios. The first option requires
treatment of the sediment to the standards provided in 40 CFR 268 (if applicable standards were
promulgated) or to levels which would render the sediments noncharacteristic if treatment
standards were not promulgated. Once adequately treated, disposal of the sediments would no
longer be regulated under RCRA-C. A second option available for characteristic wastes for which
treatment standards have not been promulgated would require dewatering of the waste and disposal
in a RCRA-C hazardous waste landfill.
RCRA-C differs from TSCA in that many specific requirements for treatment, storage or disposal
(TSD) facilities are not codified. Technical requirements for TSDs have been codified in 40 CFR
264 as Minimum Technology Requirements (MTR) and are given in Minimum Technology Guidance
(MTG) documents prepared by EPA. Site location requirements are codified with respect to seismic
considerations and floodplains (40 CFR 264.18 ). RCRA does not contain site restrictions that
would eliminate in-lake or near shore TSDs or CDFs. Under Subpart N, the hazardous waste
regulations simply specify a liner system designed to prevent any migration of wastes out of the
landfill and a leachate collection system immediately above the liner that will prevent the leachate
depth from exceeding 30 cm over the liner. These specifications form the basis for the worst-case
hydraulic isolation CDF design criteria. These general criteria are presented in Appendix E.
The ground water protection standards of Subtitle C involve the use of EPA approved health based
standards for evaluating compliance with approved environmental performance standards. Such
standards include the Maximum Contaminant Levels (MCL) established by the CWA. When no
MCLs exist, the Reference Doses (RFDs) for threshold constituents, and Carcinogenic Potency
Factors (CPFs) for non-threshold constituents are used. CPFs measure the ability of a chemical to
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cause cancer assuming a risk level of 10"6 for Class A and B carcinogens and 10~5 for Class C
carcinogens (EPA, 1986).
RCRA Subtitle D Municipal Solid Wastes (MSW) As promulgated on October 9, 1991, Subtitle
D (40 CFR 258) defined minimum landfill standards for those facilities receiving MSW and for
landfills co-disposing sewage sludge with MSW. The Co-disposal Regulations were co-promulgated
under the authority of RCRA-D and CWA. Separate regulations are being developed for sewage
sludge monofills under CWA Authority. The RCRA-D regulations are the first to clearly establish
performance objectives for the landfills. While a default composite liner is provided in Subtitle D, the
general performance criteria for a MSW landfill requires that groundwater quality be maintained
such that all constituents are at concentrations below their MCLs at a regulatory specified point of
compliance adjacent to the landfill.
1.2.2 Presumptive Remediation of Contaminated Sediments
Remediation of dredged material to remove or lower the level of contaminants may involve
combining several treatment processes to achieve cleanup objectives. Treated sediments, once
cleaned, can be used as beneficial fill material outside of a CDF or as designed components within
the CDF. For example, cleaned fine grained sediments could be used to line a CDF. The
Assessment and Remediation of Contaminated Sediments (ARCS) program has performed pilot
and bench scale demonstrations of selected technologies. A full discussion of these technologies is
presented in Appendix A of this document. It should be noted that, at present, these technologies
have not been widely implemented at full scale.
The containment of contaminated sediments in CDFs is generally viewed as the most cost effective
remediation tool. This is consistent with a parallel trend in Superfund sites where containment of the
contaminated soils or wastes has been the selected alternative in a clear majority of existing RODs.
This containment policy is expressed in recent revised Remedial Investigation/Feasibility Study
(RI/FS) procedures for contaminated municipal solid waste landfills (EPA/5407P-91/001). These
revised RI/FS procedures make containment of the waste the presumptive remedy. As with
dredging projects, the quantities of contaminated solids and relatively low contamination levels
associated with MSW landfills frequently makes current waste remediation technologies prohibitively
expensive.
1.3 Confined Disposal of Problematic Dredged Materials
While nationwide CDFs were built to dispose of clean dredged materials, within Region 5, however,
all existing CDFs were designed for the disposal of problematic dredged materials. Such facilities
are designed to retain dredged solids while allowing the carrier water to be released from the
containment area. The general conceptual drawing for this process is shown on Figure 1.2. The
principal functional components of the CDF are the containment dikes that hold the dredged
materials and a weir, or filter wall, or treatment system that allows the carrier
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PLAN
OHOGtO MATttltl.
SCCTlOM
(EM 1110-2-5027)
Figure 1.2 Conceptual Diagram of a CDF
water to decant from the CDF. The design of containment dikes is site-specific and must consider
the following factors: dike stability with respect to shear strength, settlement, seepage, erosion, and
available building materials or construction equipment. A review of specific CDF dike cross sections
and component design are presented in Section 4. The influent dredged material may be a slurry if
hydraulic dredging processes are used or a water/soil-clod matrix if bucket excavators are used.
This dredged material influent and the decanted effluent are normally characterized by the
suspended solids concentration, suspended particle size gradation, type of carrier water (fresh or
saline), and rate of flow.
The containment basin must be sized to provide an adequate volume to contain the dredged slurry
and to provide sufficient retention time for the associated water to allow solids to fall out of
suspension. Flocculent may be used to increase the rate at which solids fall out of suspension if the
site area is restricted. Weirs are designed such that the water depth above the solids can be
maintained constant as the CDF fills with sediment.
The Great Lakes CDFs were designed so that the effluent leaving the CDF has a concentration of
suspended solids less than 1 to 2 grams per liter for freshwater conditions (USAGE, 1987). Typical
effluent requirements in Region 5 are usually in terms of tens of milligrams per liter and are enforced
at those CDFs having a measurable point discharge. A more detailed discussion of the USAGE
procedure for design of CDFs is presented in Section 6.
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1.4 CDF Contaminant Pathways
The design of the CDF must be concerned with potential pathways by which the contaminant can
leave the containment system. For an upland or typical island CDF such pathways are shown on
Figure 1.3 and include
1. effluent drained through the weir or dikes,
2. leachate drained from the sediments that may move into the ground water,
3. surface water run-off,
4. plant uptake through vegetation growing within the CDF or on its dikes,
5. animal uptake in animals living or nesting within the CDF, and
6. from volatilization or wind borne migration of fine grained soils and bound
contaminants into the atmosphere.
The effectiveness of conventional CDFs to limit contaminant pathways is the focus of this document.
Performance criteria for the first five pathways are developed in Section 2. Air quality guidance for
landfills and CDF type facilities is pending. This pending guidance focuses on non-methane organic
compounds (NMOC) and will require evaluating NMOC emissions through the final cover.
eiOTURSATlON
UNSATURATEO
SATURATED
SEEPXE
W£JR
tHFIUROTOM
(USACE/EPA, 1991)
Figure 1.3 Contaminant Pathways for Upland CDF
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SECTION 2.0
DEVELOPMENT OF ENVIRONMENTAL PERFORMANCE CRITERIA for CDFs
In 1971, Region 5 of the Environmental Protection Agency (EPA) issued "Criteria for Determining
Acceptability of Dredge Spoil Disposal to the National Waters" as a first effort to identify and classify
polluted sediments in the nation's waterways for purposes of controlling dredging and disposal
operations. These ambient concentration thresholds were published before there was adequate
scientific data to define the type, quantity, and partitioning potential of contaminants which are
associated with dredged material which impact water and sediment quality at the dredging or
disposal site and, thus, become bioavailable. Sediments that failed this evaluation were considered
unsuitable for aquatic (open water) disposal and required confined disposal, i.e. placement in a
CDF. In 1977, Region 5 began to use sediment pollution criteria defined by the Great Lakes
guidelines shown on Table 2.1.
During this same time period the USAGE was developing an approach for evaluating the pollution
potential and bioavailability of contaminated dredged materials during dredging and disposal
operations. Keeley and Engler (1974) discussed the USAGE position about establishing regulatory
criteria for the disposal of clean and contaminated dredged materials in the oceans and other
aquatic bodies such as lakes and rivers. They noted that the criteria for defining environmental
protection should:
1. be meaningful and based on the best possible knowledge
2. not precede the current technical state of th» art
3. be based upon laboratory procedures that can be performed satisfactorily at routine
testing laboratories
4. attainment and implementation not be prohibitively expensive
The first guidelines for the discharge of dredged materials into waters of the United States were
issued in 1975 and were quickly followed by interim guidance manuals for discharge into navigable
waters (USAGE, 1976) and into ocean waters (EPA, 1977). The latter manual is referred to as the
"Green Book". In 1991, EPA and USAGE jointly published an update of the 1977 Green Book for
the discharge of dredged material into ocean waters (EPA/USAGE, 1991). This update was
intended to address the differences between the regulations governing disposal under CWA and
MPRSA and is specifically intended for CWA 404(b)(1) compliance determinations. EPA and
USAGE are currently drafting a guidance manual for evaluation of material proposed for discharge
in inland and near coastal waters. (Inland Testing Manual).
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Table 2.1 EPA Guideline Values for Harbor Sediment Classification
Compound/Element
Ranking
Volatile Solids (%)
COD
TKN
Oil and Grease
Lead
Zinc
Ammonia
Cyanide
Phosphorus
Iron
Nickel
Manganese
Arsenic
Cadmium
Chromium
Barium
Copper
Mercury
Total PCBs
Non Polluted
(expressed
CD
<5
<40,000
<1,000
<1,000
<40
<90
<75
<0.10
<420
<17,000
<20
<300
<3
<25
<20
<25
Moderately Polluted
in mg/kg, dry weight
5-8
40,000-80,000
1,000-2,000
1,000-2,000
40-60
90-2000
75-200
0.10-0.25
420-650
17,000-25,000
20-50
300-5CO
3-8
25-75
20-60
25-50
Heavily Polluted
unless specified) .
Q>
>8
>80,000
>2,000
>2,000
>60
>200
>200
>0.25
>650
>25,000
>50
>500
>8
>6
>75
>60
>50
>1
>10
source: Guideline for the Pollutional Classification of Great Lakes Harbor Sediments, U.S.
Environmental Protection Agency, Region V, 1977
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Because the Green Book applies to ocean and coastal waters it has not been used by Region 5 for
the Great Lakes. Region 5 has instead used a case-by-case approach using the 1977 Great Lakes
Guidelines (see Table 2.1), International Joint Commission guidelines, and other criteria to make the
decision of whether the dredged materials are polluted and thus inappropriate for open water
disposal. While the proposed Inland Testing Manual is national in scope, the USAGE North Central
Division and Region 2, 3 and 5 are also developing a Great Lakes Testing Manual.
Section 2 presents the current joint EPA/USACE sediment management strategy and then
evaluates current test procedures used to evaluate the potential contaminant pathways identified in
Section 1.4. The section concludes with a review of Region 5 Adequate Environmental
Performance and Protection (AEPP) criteria for each potential contaminant pathway.
2.1 Joint USACE/EPA Technical Framework for Dredged Material Management
Based on the USAGE decision making framework (Francingues et al, 1985) as applied to
Commencement Bay, Washington (Peddicord et al. 1986), a joint USACE/EPA guidance document
for evaluation of environmentally acceptable dredged material management alternatives was
developed (USACE/EPA, 1992). The document is intended to serve as the Technical Framework
for USAGE and EPA personnel in evaluating the environmental acceptability of dredged material
management alternatives. Three dredged material management alternatives are considered in the
joint framework: open water disposal, confined (dike) disposal, and beneficial use application. The
joint USACE/EPA dredged material management program is summarized in the flowchart on Figure
2.1. This proposed management program is divided into five major elements as follows:
Evaluation of Dredgina Project Requirements The need for the dredging project must be
established under NEPA, CWA, and/or MPRSA. Under NEPA, the initial impact assessment for the
dredging project relates to the purpose and need for the proposed action in the case of new work
and the continued viability in the case of an existing project. The needs determination under CWA or
MPRSA is specifically concerned with a justification of the necessity for dredged material disposal in
waters of the U.S. or ocean respectively.
Identification of Alternatives Under NEPA, the environmental impact of disposal options such
as CDFs, open water, and beneficial uses must be considered. The NEPA document must discuss
all reasonable alternatives even if they are beyond the capability of the applicant or lead agency
making the application. Note that NEPA does not specify performance standards but simply
requires the evaluation of alternatives.
Initial Screening of Alternatives Reasonable sediment management alternatives include those
that are practical or feasible given environmental, technical, and economic constraints. All potential
alternatives are evaluated with respect to the availability of the required and suitable disposal site,
20
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EVALUATE D«EDGkNQ AND OBPOSAL NEEDS
EVALUATION OF
DREDGING
PROJECT
REQUIREMENTS
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(EPA/USAGE, 1991, or EPA/USACE,1992)
Figure 2.1 Flow Chart Illustrating Framework for Determining Environmental Acceptability of
Dredged Material Disposal Alternatives
21
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design limitations, climatic conditions, dredging equipment availability, physical and chemical
aspects of the sediments, local interests or concerns, and known environmental regulatory (e.g.
endangered species) and economic concerns. The initial screening is based on available sources of
sediment contamination information, see Table 2.2.
Detailed Assessment of Alternatives Environmental acceptability of a sediment management
alternative must include the following:
a. evaluation of the adequacy and timeliness of existing data,
b. evaluation of the physical characteristics of the sediments,
c. evaluation of sediment contamination,
d. perform appropriate CWA testing and assessments,
e. evaluation of sediment management/control options.
The last consideration (e.) includes assessment of openwater, confined disposal and beneficial use
alternatives. This document herein concerns the assessment of confined disposal options only and
is therefore a subset of the detailed assessment of alternatives provided in the USAGE/EPA
framework.
Specific guidelines are provided in this document for evaluation of the technical feasibility and cost
of CDF alternatives. Once a Detailed Assessment of the Alternatives is completed and the CDF
alternative has been selected, the flowchart on Figure 2.2 is used for the detailed assessment of the
CDF alternative to include testing and related evaluations. This requires a site assessment of all
potential CDF locations including an evaluation of physical impacts, site capacity, and possible
management options. The primary concern of this flowchart is the short and long-term impact of
contaminated dredged material placement into the CDF and the need for additional control
measures.
Alternative Selection The selection of a preferred/proposed alternative during the NEPA EIS
phase is based on environmental acceptability, technical feasibility, costs, and other factors.
2.2 Evaluation of Contaminant Pathways
The evaluation of the impact of the disposal of contaminated dredged materials upon the local
environment is based upon a detailed laboratory testing protocol that considers each of the possible
contaminant pathways as discussed in Section 1.4. Based on the test results and analysis, the
laboratory testing program will determine if additional control measures are required for the
proposed CDF. Additional control measures such as liners, covers, and filters are covered in detail
in Appendix E and Section 7.
22
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Table 2.2 Sources of Existing Sediment Contamination Information
(draft Inland Testing Manual)
Available results of prior physical, chemical, and biological tests of the materials proposed
to be dumped.
Available results of prior field characterization studies of the materials proposed to be
dumped (e.g., physical characteristics, organic-carbon content, and grain size)
Available information describing the source(s) of the material to be dumped which would
be relevant to the identification of potential contaminants of concern.
Existing data contained in files of either the EPA or USAGE or otherwise available from
public or private sources. Examples of sources from which relevant information might be
obtained include:
Selected Chemical Spill Listing (EPA)
Pesticide Spill Reporting System (EPA)
Pollution Incident Reporting System (USCG)
Identification of In-Place Pollutants and Priorities for Removal (EPA)
Hazardous waste sites and management facilities reports (EPA)
USAGE studies of sediment pollution and sediments
Federal STORET, BIOS, CETIS, and ODES databases (EPA)
Water and sediment data on major tributaries (USGS)
NPDES permit records
Fish and Wildlife Service
CWA 404(b)(1) evaluations
Pertinent and applicable research reports
MPRSA 103 Evaluations
Port Authorities
Colleges/Universities
Records of state agencies (e.g.,environmental,water survey)
Published scientific literature
CERCLA/RCRA Facility Files
23
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ENTER FROM FLOWCHART Vl TO EVALUATE
CON FINED DISPOSAL
DETERMINE CHARACTERISTICS OF ALL POTENTIAL
CONFINED SITES
EVALUATE DIRECT PHYSICAL IMPACTS AND
SITE CAPACITY
EVALUATE
MANAGEMENT OPTIONS
OPERATIONAL
MODIFICATIONS
DEWATERING
SITE MANAGEMENT
OTHERS
1
t
EFFLUENT
CONTROLS
TREATMENT
OPERATIONAL
MODIFICATIONS
OTHERS
EVALUATE CONTBOL MEASURES FOR
CONTAMINANT PATHWAYS Of CONCERN
i
SURFACE
RUNOFF CONTROLS
PONDING
TREATMENT
OTHERS
t
LEACHATE
CONTROLS
COVERS
UNERS
TREATMENT
OTHERS
t t
PlANT UPTAKE
CONTROLS
COVERS
SELECTIVE
VEGETATION
OTHERS
AMUAL UPTAKE
CONTROLS
COVERS
OTHERS
(EPA/USACE,1991 or EPA/USACE.1992)
Figure 2.2 Flow Chart Illustrating Framework for Testing and Evaluation
For Confined (Dike) Disposal
24
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This Page Left Blank
25
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2.2.1 Effluent Discharge Quality
The large volumes of fluids generated during dredging may contain undesirable levels of dissolved
contaminants and suspended fine solids with adsorbed contaminants. The modified elutriate test
(Palermo, 1984) is the current method which the USAGE uses to predict effluent quality from a CDF
(USAGE/EPA, 1992). This is a modification of the standard elutriate test used for assessment of
aquatic disposal of dredged material.
A review of the standard elutriate test is presented here to aid in understanding the transition
represented by the "modified" elutriate test. The USAGE has always based its criteria on the change
in ambient water quality (dissolved chemical concentrations) that might be expected during dredging
and disposal in a CDF. The compliance of a dredged material operation with State Water Quality
Standards (WQS) is assessed by the elutriate test which is designed to simulate the
dredging/disposal process. A schematic diagram of the original elutriate test (Keeley and Engler) is
presented in Figure 2.3 as designed for the disposal of hydraulically dredged material. As noted in
the diagram, four volumes of disposal site water and one volume of contaminated dredged material
are shaken vigorously in a beaker for 30 minutes to simulate hydraulic dredging and to allow for the
exchange of contaminants from the solid phase (adsorbed organics and metals) to the dissolved
phase. Also, prior to mixing the water with sediments, the dissolved concentrations of pollutants in
the disposal site water are measured and listed as Xv After shaking the sediment/water
suspension, the mixture is allowed to settle for one hour. The supernatant is then filtered to remove
particles and analyzed for the same chemical constituents previously determined and listed as X.
While test simplifies the complex interaction between polluted sediment and water, it has shown that
there is little migration from the solid to dissolved phase.
(SETTI
"
SETTLE FOR
HR
CENTRIFUGATIONOR
0.45mm FILTRATION
-^ \
CHEMICAL ANALYSIS
DISSOLVED CONCENTRATION
(Keeley and Engler, 1974)
Figure 2.3 Elutriate Test
26
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The modified elutriate test, as summarized in Figure 2.4, was developed by USAGE to be a more
realistic laboratory simulation of CDF effluent quality during hydraulic disposal of dredged material in
open water or within a CDF. The test involves mixing contaminated sediment and water from the
dredge site in proportion to the expected CDF influent concentration as influenced by the dredging
method. The mixture is then aerated and settled in a column. Modifications to the test can be made
to simulate transport and deposition for an estimated CDF retention time (Averett et al, 1988 and
Palermo et al, 1988). The unfiltered supernatant (effluent) is subjected to chemical analysis to
define the concentration of the contaminants associated with the total suspended solids (TSS).
Similarly, a chemical analysis is performed on the filtered water to determine the concentrations of
contaminants dissolved in the water. This allows prediction of both the dissolved and the total
concentration of contaminants in the effluent.
(MIX UOMMNT MtO MATIN TO
CX1CTCD IMUMHT CDNCfMTMATION
T
/ SETTLE FOM IXMECTID WEAN FIELD \
I HETf NTKM TIM Uf TO M NH MAXIMUM j
I fXTHACTSAMPLJ AMD
(Palermo, 1989)
Figure 2.4 Modified Elutriate Test
The modified elutriate test is generally used with a parallel column settling test to predict actual
effluent TSS as outlined in Figure 2.5. The estimated total concentration of effluent contaminants is
compared to State water quality standards, (WQS). If the effluent does not meet the State WQS
standards, the USAGE can then propose the use of a mixing zone to further dilute the effluent as
part of the CDF design.
While the modified elutriate test provides conservative estimates of contaminants within the effluent,
the bulk quantities (mass released) of contaminants released from a CDF are highly dependent
upon the volume of dredging fluids generated during dredging. The percentage of dredging fluids by
27
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EVALUATE PERTINENT PROJECT DATA
ON DREDGE AND DISPOSAL AREA
SAMPLE SEDIMENT AND I
DREDGING SITE WATER I
PERFORM MODIFIED
ELUTRIATE TESTS
PERFORM COLUMN
SETTLING TESTS
ESTIMATE DISSOLVED CONCENTRATION
OF CONTAMINANTS AND FRACTION
IN SUSPENDED SOLIDS
ESTIMATE SUSPENDED SOLIDS
IN DISPOSAL AREA EFFLUENT
ESTIMATE TOTAL CONCENTRATION OF CONTAMINANTS
IN DISPOSAL AREA EFFLUENT
APPLY MIXING ZONE AND COMPARE
WITH STANDARDS OR CRITERIA
(Draft, Inland Test Manual)
Figure 2.5 Effluent Quality Predictive Technique
weight can range from more than 90% for hydraulic methods, e.g. using a cutterhead dredge, to less
than 20% using clam-shell excavations. For a hypothetical annual dredging volume of 200,000
cubic yards of the highly contaminated sediments associated with Indiana Harbor, the
USACE(1987b) estimated the quantities of PCBs expected to be released with the effluent for three
CDF filling scenarios including hydraulic transfer from scow, direct pumping from dredge site using a
matchbox type dredgehead and mechanical placement. The projected annual PCBs released for
these three methods relative to a common size CDF are 6.3 kg, 4.2 kg and 0.0027 kg, respectively.
Ironically, methods of dredging that minimize contaminant transport at the site of dredging can lead
to a maximum potential for contaminant release at the point of discharge from the CDF and
ultimately into the local environment. For example, the use of a cutterhead dredge minimizes the
generation of turbidity and the potential for contaminant migration at the dredging site. However, the
high water to solids effluent produced by the cutterhead hydraulic dredging does produce a potential
for contaminant migration in the effluent.
The effluent from a CDF is generated by both the supernatant that remains after the dredged
material falls out of suspension and from rainfall run-off coming from dredged material that rises
above the water elevation. The quality of the effluent is influenced by type and quantities of
pollutants, sediment mineralology and organic content, and the dissolution kinetics discussed below.
Organic Contaminants An alternative approach to evaluate the relationship between sediments
and bioavailability of toxic organic contaminants is the equilibrium partitioning (EqP) method. The
EqP approach relies on established water quality criteria to assess sediment toxicity. The first basic
assumption of the EqP approach is that sediment toxicity is correlated to the concentration of the
contaminants in the interstitial water and not to the total sediment concentration. The second basic
28
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assumption is that contaminants partitioned between the interstitial water and the sediment sorbents
(i.e. organic carbon) are in equilibrium. Such equilibrium concentrations are significantly larger than
developed in the elutriate tests. Therefore, for a given contaminant, if the total sediment
concentration, the concentration of sorbent(s), and the partitioning coefficient are known, then the
interstitial pore water contaminant concentration can be calculated. Given the third assumption that
organic carbon is the significant sorbent, the contaminant concentration can be predicted based on
the total organic compound (e.g. TOC normalization).
Metal Contaminants Of particular recent interest is research into the relationship between
sediment sulfide content and bioavailability of toxic metals. Studies by DiToro et al. (1990), Carlson
et al. (1991), and Ankley et al. (1991) have shown that sulfide content of freshwater and marine
sediments is a predominant determinant of metal toxicity. This is based on the fact that many toxic
metals form insoluble sulfides in anoxic or reduced environments (e.g. cadmium, copper, lead,
mercury, nickel, and zinc) and most freshwater and marine sediments have significant sulfide
contents. Note that this includes uncontaminated sediments. These researchers examined acid
volatile sulfide (AVS) content of sediments, the solid phase sediment sulfides (FeS and MnS, H2S,
HS, and S2'2) that are soluble in cold acid, and the concentration of simultaneously extracted metals
(SEM) using the ratio [SEM]/[AVS]. AVS binding of metals reduces their bioavailability by
decreasing metal solubility and is a precursor to formation of more insoluble pyritic sulfides (e.g.
FeS2). Formation of pyritic metal sulfides is one mechanism of potential permanent removal of toxic
metals. DiToro et al. (1990) measured [AVS] of marine sediments in relation to cadmium toxicity to
three species of amphipods. They found that [AVS] is the sediment phase that determines the LC-
50 for cadmium and also that correlations occurred between mortality and interstitial water metal
activity. Ankley et al. (1991) studied cadmium and nickel in estuarine sediments in 10-day exposure
tests with an amphipod and oligochaete species. In this study, molar [SEM (cadmium and
nickel)]/[AVS] ratios greater than one were consistently toxic to the amphipod (Hyallela azteca) and
ratios of less than one were not. Metal availability was apparent through bioaccumulation in the
oligochaete worm (Lumbriculus variegatus) when [SEM]/[AVS] ratios exceeded one. Freshwater
sediments were spiked with cadmium and tested by a 10-day exposure with the same species of
oligochaete worm, and the snail Helisoma so. (Carlson et al., 1991). Here again, toxicity was not
observed when the cadmium/AVS ratio was less than or equal to one.
Metal bioavaiiability is decreased by AVS, which acts as a sink for metals as long as the sediment
remains anaerobic and the redox potential is too low to allow for oxidation of sulfides. Decreasing
solubility of metal sulfides coincides with an increased AVS affinity for metals, that is
Mn
-------
notes the importance of microbial processes to sediment [AVS], considering this a critical need in
future research. General rules of thumb for sediments were:
[metal]/[AVS] < 1 sediment has little toxicity;
1 < [metal]/[AVS] < 10 sediment has little to high toxicity
[metal]/[AVS] > 10 sediment is highly toxic
Copper may be an exception to this rule due to its affinity to also bind to organic compounds, and
most of this research was performed on marine and lake sediment (i.e. high in Fe and aluminum
oxides).
2.2.2 Surface Water Run-off Quality
Concerns regarding surface water run-off from the dredged material in the CDF begin when the
elevation of the dredged material exceeds that of the water in the CDF. This concern can be
mitigated by an adequate residence time for the supernatant (e.g. water draining from the dredged
materials) and run-off waters in the CDF such that the fines settle out and are not carried out of the
CDF by the effluent. Final contours of sediment within the CDF can exceed the elevation of
perimeter dikes. Thus, there is the long-term potential for sediment and contaminant mobility with
the runoff water if the dredged material is not properly managed.
The quality of surface runoff water within a CDF can be expected to vary with time as a result of the
changing physicochemical condition of the dredged material. When initially placed in a CDF, the
dredged material is saturated, reduced, anaerobic and of neutral to slightly basic pH. However,
dredged material placed above the zone of saturation within the CDF are subject to drying. This
promotes aerobic microbial degradation or volatilization of organic components, oxidation of some
metals and sulfides and changes in pH (usually lower and more acidic depending on the mineral
composition of the dredged material). This reduction in pH can increase the solubility of metals and
organic contaminants, leading to release of the contaminants (see Appendix A).
A laboratory testing protocol has been developed by the U.S. Army Waterways Experiment Station
(WES) to simulate the complex process of rainfall runoff (Lee and Skogerboe, 1983; Lee et al 1991).
The WES surface runoff simulator is shown in Figure 2.6. The test protocol requires a large
sediment sample from the dredge site to be placed in the soil lysimeter in the saturated reduced
state. At various stages of the drying process, rainfall events are applied to the dredge material and
surface runoff water samples are collected for analysis of water quality parameters. Rainfall
simulations are performed several times over the full range of air drying. These results have been
shown to accurately predict surface runoff water quality which can be compared to water quality
30
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RAINFALL SIMULATOR-
VARIABLE SLOPE
AND DEPTH SOIL
LYSIMETER
RUNOFF QUANTITY AND
QUALITY MONITORING
(Leeetal., 1991)
Figure 2.6 Surface Runoff Evaporation Simulator
standards and, thus, determine the need for runoff water treatment or the need to apply control
measures to the CDF (e.g. an engineered final cover). This apparatus can also be used to evaluate
control measures such as lime treatment, soil covers and plant stabilization. Section 7 presents
such design considerations for an engineered final cover.
2.2.3 Plant Uptake
Most dredged sediments contain large amounts of nitrogen and phosphorus which promote vigorous
plant growth. As a result, plants are easily established in a CDF following placement of sediments.
When contaminated dredged materials are placed in the CDF, there is the potential that
contaminants will move into the food chain from bioaccumulation in the plants. A summary of
sources and pathways of toxic trace elements to plants is presented on Table 2-3. Organic
contaminants typically have large molecules that will not pass through the cell walls of plants, thus
limiting the plant uptake of organics. Also, because most contaminated dredged materials contain a
suite of pollutants they may interact to affect biological systems.
The USAGE has developed a plant bioassay test protocol (Folsom et al, 1981; Lee et al, 1991)
which has been applied to freshwater and marine sediments. For freshwater sediments, the test
protocol uses Cyperus Escalantus (yellow nutsedge) as an index plant. This plant is grown in
buckets filled with contaminated sediments from the dredge site under conditions that simulate the
CDF environment. Plant growth, phytotoxicity (growth reduction) and bioaccumulation are monitored
during the test in the apparatus shown in Figure 2.7. A chemical analysis is performed on plants
31
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Table 2.3 Sources and Pathways of Toxic Trace Elements to Plants
Sb* As Be B Cd Cr Co Cu Pb Hg Ni Se Sn V
Uptake by roots
A. Soil or groundwater x x
B. Fallout to soil from air pollution x x
C. Sewage sludge soil amendments x
D. Biocides applied to soil and/or seed x
E. Surface water contamination x
F. Fertilizers x
G. Industrial pollution x
Uptake bv leaves and stems
A. Pollutant fallout from industrial sources x x
B. Pollutant fallout from auto emissions
C. Biocide applications to plants x
D. Pollution fallout from incineration of fossil x x
xxxxxxxxxxxx
xxxxxxxxxx x
XX X X X X X
XX XXX X
XX X
XX X XX X
XX X XX X
X XXXXXXXX
X
XX XXX X
xxxxxxxxxxxx
fuels and refuse
32
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Soil Moisture Tenilomeler
Cyparus ticultnlus
YELLOW NUTSEDGE
22.7-1 Bucket
7.0-1 Bucket
Tuberj
Dredged or Fill Material
Washed Quartz Sand
Polyurelhane Sponge
r2.54-cm PVC Pipe
Figure 2.7 Plant Bioassay Procedure
(Leeetal., 1991)
harvested from the test buckets. The level of chemicals present in the plants can be compared to
allowable threshold levels such as FDA crop limits. When limits are exceeded, the sediment
management strategy would invoke control measures such as restricted placement of polluted
dredge materials in the CDF to minimize exposure, such as placement of clean surface layers,
limiting plant growth to desirable plant species, etc. Dredged materials producing excessive plant
uptake will require designed control measures (e.g. an engineered final cover).
2.2.4 Animal Uptake
Both upland and inlake CDFs are invaded and colonized by many animal species after each phase
of dredge material placement. The type of wildlife depends to some degree on the nature of the
setting; particularly whether the CDF filling stage exhibits dry pastoral or marshlike environment.
Given the long life of many CDFs, significant animal colonies may be established during various
interim phases of dredged material placement. Surface ponds may exist during the operational life
of a CDF. Such ponds can support the presence offish and benthic organisms. Bioavailable
metals and organic compounds can then be transferred from the dredged material to fish or benthic
organisms. The contaminants then can move quickly up the food chain. Such interim uptake
problems can be reduced by the application of clean dredged material to the surface of problematic
dredged material. Such "clean" interim covers are discussed in greater detail in Section 7.
Hierarchal food chain development is dependent on the lowest form of plant and animal species.
Contaminants that are bioavailable at small concentrations to the lowest species may be magnified
during migration up the food chain. A summary of the sources and pathways of toxic trace elements
to animals is presented on Table 2-4. The test protocol used by the USAGE to evaluate animal
33
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Table 2.4 Sources and Pathways of Toxic Trace Elements to Animals
Sb* As Be B Cd Cr Co Cu Pb Hg Ni Se Sn V
Terrestrial
A. Breathing Contaminated air
B. Eating contaminated plant or animal
tissue
C. Drinking contaminated water
D. Licking or preening fur or leathers
E. Receiving therapeutic drugs (domestic
animals)
F. Eating biocides or poison baits
xxxxxxxxxxxxxx
xxxxxxxxxxxxxx
xxxxxxxxxxxxxx
X
Aquatic
A.
B
C.
D
E.
F.
G.
Metal in water
Runoff and fallout
Sewage and industrial waste outfalls
Mine tailings or smelter waste leachate
Contaminated plants, animals, or
sediment
Biocides or runoff
Lead shot
XXX
X
X X
X
X X
X
X X X X X X
XX XXX
X X X X X X X
XX XXX
X X X X X X X
X X
X
XXX
XXX
X X
X
XXX
X
X
X
X
*Key: Sb = Antimony; As = Arsenic; Be = Beryllium: B = Poron; Cd = Cadmium; Cr = Chromium; Co = Cobalt;
Cu = Copper; Pb = Lead; Hg = Mercury; Ni = Nickel; Se = Selenium; Sn = Tin; V = Vanadium
(Ref Jenkins, 1981)
34
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uptake of contaminants from dredged sediments was borrowed from the European Economic
Commission (EEC). This test was used by the EEC to determine the hazardous nature of
manufactured chemicals prior to sale in Europe.
6-Inch PVC
NyUx M»«h
15-em PUilglatt Tub«
Dr*dg«d MlUriil
E*nhworm>
340/7 Nyt«« M««h
15-cm PVC
Walar R«««r»olr
(Leeetal., 1991)
Figure 2.8 Earthworm Bioassay Procedure
As adapted by the USAGE, the EEC test involves placement of ordinary earthworms in a container
filled with polluted dredge materials as shown of Figure 2.8. The material is kept in moist, semi-
moist, and air-dried conditions to simulate the expected range of CDF environments. For a period of
28 days, the earthworms are monitored for toxicity and bioaccumulation of contaminants. Lee et al
(1991) noted that this test protocol can indicate potential environmental effects for dredged material
placed in upland environments. It has also been shown useful for identifying bioavailable metals and
organic contaminants. Contaminant problems are identified by comparing body burdens with
allowable FDA limits. Contaminated sediments producing excessive uptake in the earthworms will
require CDF control measures for the dredge materials (e.g. an engineered final cover).
2.2.5 Groundwater Leachate Quality
When a dredged material is placed in an upland CDF or above the water elevation in an in-lake
CDF, a downward hydraulic gradient develops as the slurry consolidates. This gradient forces
leachate into the underlying strata. The degree of leachate penetration into the underlying strata is
influenced by the site hydraulics. For instance, CDFs located at near-shore settings may be within a
zone of groundwater discharge that would limit or prevent leachate penetrations. Following
consolidation, water seepage through the sediment may continue to generate leachate due to
surface infiltration of rainwater. Movement of contaminants due to a hydraulic gradient is termed
advective transport. Simultaneously with the advective transport, the contaminants undergo
molecular diffusion. This process is more significant through fine grained sediments due to their low
35
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hydraulic conductivity. Diffusion of contaminants occurs due to contaminant concentration gradients
and typically at rates so slow that it can be neglected. The quantity of leachate can be accurately
predicted from advective flow theory if the site and CDF hydrogeoiogical parameters are known.
However the quality of leachate is affected by the type and quantities of pollutants, sediment
mineralogy and organic content, equilibrium concentration of contaminants and pH of the pore fluid,
and dissolution kinetics to name a few. Many of these parameters that influence leachate quality
are influenced by the geochemical factors that change as the CDF is being filled.
There is presently no routinely used leachate testing protocol to define the type and quantity of
contaminants carried by ieachate from dredged material. There are a number of standardized test
methods which could simulate leachate generation from both consolidation and percolation. For
example, a soil/sediment press as shown in Figure 2.9 (ASTM.1992) is commonly used to extract
pore fluids from marine sediment samples. Contaminant concentrations in such pore waters will
generally be at equilibrium. This test could be used to simulate leachate generation from soluble
contaminants during consolidation. Additionally, the soil press sample can be extracted from the
press for use in a flexible wall permeameter cell to simulate leachate generation due to percolation.
The fluids removed from the dredged material by either a soil press or permeameter could be
subjected to analysis for typical water quality parameters. Field samples of pore water fluids can
also be obtained using cone penetrometers equipped with porous stone sampling ports. An
example of such field equipment is shown on Figure 2.10. The cone is pushed into the sediments
hydraulically. Once at the depth a sample is required, the cone shaft is withdrawn slightly to expose
the porous stone sampling part. At this time, an inner shaft is pushed downward to break a rubber
septum that separates the porous stone and a glass vacuum sample tube. A sample of the pore
water is then drawn by the vacuum into the glass tube. The pore water sample is then recovered by
withdrawal of the cone penetrometer. Pcrs water samples obtained in this fashion are filtered and
represent the actual soluble contaminant present in the subgrade.
The USAGE has applied a sequential batch leaching procedure and a column leaching test to
evaluate confined disposal of dredged material from Indiana Harbor; Everett Harbor, Washington;
and New Bedford Harbor, Massachusetts ( USAGE, 1987; Palermo et al, 1989; Myers and Brannon,
1988). The USAGE has not yet endorsed a leachate test for routine testing and continues to
perform research and evaluation testing on leachate generation.
2.2.6 Water Column Discharge Quality
During much of the operational life of an in-water CDF, the surface of the dredged material is below
the water level within the CDF. The surface water can act as a host to aquatic animals and provides
a contaminant uptake pathway. An interim cover of clean dredged material may be required to limit
this short-term contaminant pathway. If required, an interim cover placed over the contaminated
sediments must be able to limit the advective movement of contaminants vertically through the
interim cover and biological uptake of the contaminants. It is assumed that the sediments and cover
are saturated and in direct communication with the water column. The impact of contaminants
36
-------
RAW
TEFLON DISK
CYLINDER
STAINLESS STE
WIRE SCREEN DISK
RUIIER (NEOMENC)
WASHER
ASE
EFFLUENT PUSAAE
RUIIER (MCOPftCNE) DISK
^ERFORATEO PLATE
(FILTER PAPER SUPPORT)
FILTER MOLOCM
CFFLUENT PASSAGE DCAMEO
TO FIT NOSC OF SYRINGE
SYMINGC
(ASTM Method D4542)
Figure 2.9 Soil Press for Sediment Leachate Sampling
OMOOtO UATtBUU.
trtut
(Draft Inland Test Manual)
Figure 2.10 Factors Influencing CDF Effluents
37
-------
moving through the interim cover have been assessed using small and large scale laboratory water
column discharge reactor units (Brannon et al, 1986, and O'Connor and O'Connor, 1983). These
units were designed to assess the effectiveness of subaqueous capping at open water sites, but the
same principles apply for overlying soil covers for CDFs. The effectiveness of the cover is assessed
by following the movements of chemical contaminants and microbial spores found in the
contaminated sediments into the overlying water column and by monitoring the biological uptake of
chemical contaminants by clams and polychaetes. Such tests on Dutch Kills sediments from New
Jersey indicated that as little as 10 cm of sand cover was effective in isolating the water column but
50 cm was required to eliminate biological uptake. No test standards currently exist for the water
column uptake reactor test.
2.2.7 Airborne Loss of Contaminants
Contaminants can migrate from the surface of dredged materials that are above the waterline due to
direct volatilization of contaminants from the surface of the dredged materials or attached to wind
blown soil particles. Both airborne pathways show increase contaminant loss with increasing wind
duration and velocity.
The volatilization of contaminants from the dredged materials is governed by Henry's Law; the
weight of any gas that will dissolve in a given volume of a liquid, at constant temperature, is directly
proportional to the pressure that the gas exerts above the liquid. Henry's Law is expressed as
follows:
Cequ.l = O Pgas
Where Cequil is the concentration of gas dissolved in the liquid at equilibrium, pgas is the partial
pre?sure of the gas above the liquid, and a is the Henry's Law constant for the gas. The partial
pressure of the gas above the dredged materials is influenced by air temperature, wind, and
atmospheric pressure.
Wind erosion is a mechanism by which fine particulate matter and soil at the surface become
airborne. Soil grain size and shape influence a particle's ability to become airborne. Additionally,
particulate matter having an effective aerodynamic diameter less than 10 microns (PM-10) is
regarded as the largest particle size that can directly penetrate the human respiratory system
(Perera and Ahmed). PM-10 also applies to standards established by EPA for acceptable levels of
fine particulate matter in air (40 CFR 50).
2.3 AEPP Evaluation Criteria For CDFs
Prior to reviewing AEPP criteria for potential contaminant pathways from a CDF, it is important to
understand the difficulties associated with even the identification of problematic dredged materials.
38
-------
The current confusion regarding sediment testing guidelines and criteria were expressed by the U.S.
General Accounting Office as follows (GAO, 1992):
According to EPA, some scientists believe that the 1975 testing guidelines EPA
developed in conjunction with the Corps under section 404(b)(1) of the Clean Water
Act - guidelines the Corps is currently using for disposal decisions on dredged material
- are technically inadequate. However, Corps headquarters officials maintain that the
guidelines have evolved substantially, have been tested thoroughly, and are adequate.
Both the Corps and EPA have conducted detailed research on contaminated sediment,
but the agencies have not always agreed on how the research should be used to
determine which sediment needs confinement. The lack of agreement occurs
generally because of the difficulty in establishing clear cause-and-effect relationships
between the contaminant concentration in sediment and a biological impact on humans
and wildlife.
In 1991, EPA and USAGE jointly published testing guidance for the discharge of dredged material
into ocean waters (EPA/USACE, 1991). Currently EPA and USAGE are developing a similar testing
guidance for evaluation of material proposed for discharge to inland and near coastal waters
(referred to as Inland Testing Manual).
The environmental performance of a CDF should be verified by a monitoring program that assesses
the success of control measures for each of the contaminant pathways that are identified during the
testing protocol, see Section 8. Evaluation criteria are required to serve as the standard by which
the test results from laboratory simulations and field monitoring are evaluated. While finalized
evaluation criteria are not currently available for all contaminant pathways, there are sufficient data
in the literature from EPA, FDA, the European Economic Community, and research data to help with
the decision making process. Table 2.5 summarizes the type of existing information that might be
useful for evaluating each contaminant pathway. Specific evaluation criteria are discussed in this
section and presented in greater detail in Appendix B. The contaminants or nutrients of concern
must be selected on a case-by-case basis. Contaminants of interest are those that have FDA limits,
are the subject of state fisheries advisories, or have EPA water quality criteria.
2.3.1 Effluent AEPP Criteria
The factors influencing effluents from CDFs are shown on Figure 2.11. An unacceptable effluent
discharge is one in which the concentration of any dredged material constituent, after allowance for
mixing, exceeds applicable State water quality standards (WQS). Effluents from a CDF may be
discharged as a point source through a weir system or filter cells, or as a non-point sourceflow
through the dikes. Assuming that the sediments have been established as potentially contaminated,
the modified elutriate and column settling tests are used to predict effluent quality as shown on
Figure 2.5. The standards used for final comparison include State WQS as required under Section
401 oftheCWA.
39
-------
Table 2.5 Evaluation Criteria for Contaminant Pathways
Pathway Criteria
Effluent . EPA Water Quality Criteria (Table B1)
State Water Quality Standards
CWA Mixing Zone Criteria
State Mixing Zone Criteria
Run-Off EPA Water Quality Criteria (Table B1)
Plant Uptake Research Results (Table B2)
Animal Uptake FDA and European Action Levels for
Foodstuffs (Table B3)
Leachate EPA Drinking Water Standards
(Table B4)
Air Emissions Pending EPA Air Quality Standards
2.3.2 Surface Water Run-Off AEPP Criteria
The final closure of the CDF must ensure that water run-off from the facility meets the same criteria
discussed above for effluent discharge. Additionally, many states will require a sediment control plan
and potential discharge control structures, e.g. sedimentation ponds, to limit erosion and siltation of
adjoining bodies of water. As discussed in Sections 3 and 4, current CDFs Jo not have a standard
approach to closure but are consistently very flat in profile. Such minimal grades provide for control
of water run-off related erosion at the expense of increased infiltration potential. Site specific testing
can be performed using the test device shown on Figure 2.6 and described by Lee and Skogerboe
(1983).
2.3.3 Plant Uptake AEPP Criteria
The potential for movement of unacceptable levels of contaminants from the dredged material into
the environment through plants and eventually into the food chain must be restricted. Appropriate
40
-------
management strategies therefore are formulated to place problematic dredged material to minimize
plant uptake. The management strategies control and manage plant species on the site so that
desirable plant species that do not uptake and accumulate contaminants are allowed to colonize
the site, while undesirable plant species are removed or eliminated. Plant uptake can be limited
during interim periods of the CDF life when a significant surface area of problematic dredged
material may be exposed for years. Therefore control of plant uptake will be considered throughout
the life of the CDF and not just after final closure. Limits on plant uptake can be established using
criteria presented on Tables B-4 and B-5 using control mechanisms discussed in Section 5.2.1.
2.3.4 Animal Uptake AEPP Criteria
A potential for animal uptake of unacceptable levels of contaminants from dredged material may
exist. Appropriate management strategies therefore need to be formulated that consider the
ultimate environment in which the dredged material is placed, the anticipated ecosystem
developed,and the physico-chemical processes governing the biological availability of contaminants
for animal uptake. Interim periods during the operational life of the CDF may be more critical than
after the final closure. Surface ponds created during the filling of a CDF may support aquatic life
that will provide the basis for contaminant uptake through the food chain via visiting avian and
terrestrial species. Limits on animal uptake can be established using criteria presented on Table B6
and control mechanisms discussed in Section 5.2.2.
2.3.5 Groundwater Leachate AEPP Criteria
Pollutants that are dissolved in the excess water of the dredged sediments can contaminate the
underlying groundwater. Such migration of contaminants may be caused by pressure gradients that
develop in the pore water during consolidation of the dredged sediments or at sites that are natural
ground water recharge zones and result in advective transport of the contaminant to the
groundwater or by diffusion of the contaminant caused by concentration gradients.
Contamination of underlying groundwaters is also a design consideration in common landfills. For
instance, the recent promulgation of RCRA part 257.3-4 provides groundwater contamination criteria
for solid waste landfills. These revised regulations state that the solid waste facility shall not
contaminate underground drinking water sources beyond its boundary or point of compliance. For
purposes of this requirement, contamination is defined as concentrations of substances exceeding
maximum contaminant levels (MCLs) developed by EPA under Section 1412 of the Safe Drinking
Water Act (SDWA) or existing ambient groundwater quality. The list of current MCLs is given on
Table 2.6. EPA is in the process of amending this list so adjustments to the MCLs can be
anticipated. The point of compliance is usually taken as the water table at the nearest monitoring
41
-------
Table 2.6 Maximum Contaminant Levels (MCLs) - SDWA
Chemical
Chromium (hexavalent)
2,4-Dichlorophenoxy acetic acid .
1 ,4-Dichlorobenzene
1 ,2-Dichloroethene
1,1-Dichloroethylene
Endrin
Fluoride . . .
Lindane
Lead .
Mercury
Methoxychlor
Nitrate
Selenium
Silver
Toxaphene .
1 1,1-Trichloroethene
Trichloroethylene
2,4,5-Trichlorophenoxy acetic acid . . .
Vinyl chloride
CAS No.
7440-47-3
94-75-7
106-46-7
107-06-2
75-35-4
75-20-8
7
58-89-8
7438-82-1
7438-87-6
72-43-5
7782-49-2
7440-22-4
8001-35-2
71-55-6
79-01-6
93-76-5
75-01-4
MCL
(mg/l)
005
0 1
0.075
0005
0.007
0.0002
40
0004
0.05
0.002
0.1
10.0
0.01
0.05
0.005
0.2
0.005
0.01
0.002
well. In addition, many states have non-degradation and cleanup criteria that may be orders of
magnitude more stringent than MCL levels. Such small levels of acceptable contaminant presence
are commonly due to biologically concentrating contaminants (or bio-magnification) that result in
toxicity concerns.
2.3.6 Airborne Loss AEPP Criteria
Past research has examined odor control problems at CDFs but has not developed models for
evaluating the nature and quantity of volatile emission of contaminants from dredged materials.
New Source Performance Standards (NSPS) are now being promulgated under the Clean Air Act
(CAA). While NSPS for CDFs are not currently available, they have been promulgated (May 30,
42
-------
1991 Federal Register) for Municipal Solid Waste (MSW) landfills. The proposed MSW
performance standards focus on the quantity of non-methane organic compounds (NMOC) released
by the landfill annually. The proposed NSPS establishes a maximum annual emission of 150 metric
tons per year for a landfill. A tiered evaluation system, see Figure 2.11, is proposed to evaluate the
actual NMOC discharge for a given MSW landfill. Tier 1 evaluation uses an EPA computer model
that over estimates NMOC release. Tier 2 and 3 evaluations require varying degrees of field
measurements to develop more accurate site specific volatization quantities.
The 1990 amendments to the Clean Air Act (CAA) established three broad categories of airborne
pollutants:
Releases of volatile organic compounds (VOCs) are controlled because they react to form
smog,
Routine releases of 189 hazardous air pollutants (HAPs) are limited to protect both human
health and the environment; and
Accidental releases of extremely hazardous substances (EHS).
The first two categories of airborne pollutants are directly applicable to potential releases from a
CDF. The CAA requires every major source (e.g. producing more than 10 tons of emission) in the
United States that omits a regulated pollutant to obtain an operating permit and pay an annual
emissions fee for each regulated pollutant. Additionally, the CAA requires that new sources must
not lead to a significant deterioration of the one existing air quality. The prevention of significant
deterioration (PSD) is particularly applicable to sites having air quality cleanei than national
standards.
43
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No
Landfill does
not require
control
. !<«; Tfer 1 -
Using'tendfltl characteristics and default
valued ifp"r£KfLo, and concentration of
nohme'thane organic'- compounds
(NMOC)," determine if the landfill is ex-
empt from control requirements.
landfill closed?
v Repeat Tier 1 each
Yes year.
Yes
Landfill does
not require -
control
No
Exempt from control?
No Install Controls
. Redeter-
I v-- -»' -«*JV"*-1
wexernpt frbm control
-"
.^. ... ^.-
con(»Rffa{ion.
Is landfill closed?
QT Total NMOC emission
rate from the landfill
(Mg/yr)
k Landfill gas generation
constant (1/yr)
L0 Methane generation
potential (mVMg)
M! Mass of refuse in the ilh
section (Mg)
t Age of the i'h section
(yrs)
CNMOC Concentranon of NMOC
(ppmv)
Yes
Repeat Tier 2 updating
the NMOC concentra-
tion data at the speci-
fied intervals.
Exempt from control?
Yes
No
Landfill does
not require -
control
Install Controls
^.-^;/.. - Tiers-..--- - ,-
^betermfne the landfill gas generation rate
t using EPA test procedures. From the site-
speclflcHk and NMOC concentration data,
redetermine if control is required.
Yes
Is landfill closed?
Repeat Tier 3 updating
the NMOC concentra-
tion data at the specif-
ic intervals. Updating
the rate constant value
is not required.
Exempt from control?
Yes
Install Controls
(Federal Register, Jan, 1993)
Figure 2.11 Tiered Gas Emission Model (RCRA-D)
44
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SECTION 3
DREDGED MATERIAL IN THE GREAT LAKES
3.1 Navigation Dredging by the USAGE
Prior to the 1960s, economic considerations typically dominated the selection of dredged
material disposal alternatives, with little regard for environmental impact. This generally meant
open water disposal of harbor and channel sediments, and land (or wetland) impoundment of
river sediments. In the mid-1 960s, questions were raised about the effects of dredging on
water quality in the Great Lakes. Open water disposal of contaminated dredged material was
openly criticized and USAGE, in cooperation with the Federal Water Pollution Control
Administration (the predecessor of EPA), studied and evaluated the alternative approaches to
the disposal of contaminated dredged materials. The primary concern at first was to control
nutrient loadings such as nitrogen and phosphorous and to limit sediment transport.
The studies included a two-year, 1 2-volume report by the Corps entitled "Dredging and Water
Quality Problems in the Great Lakes" (USAGE, 1969). This report reviewed dredging and
disposal practices, examined the impact on water quality and recommended some
modifications and control measures. This study and many subsequent studies found that the
effects of dredging and disposal activities were localized, short-lived and difficult to measure in
terms of impact on water quality and biological communities. However, the nature of dredging
and disposal operations is such that very high levels of dilution occur which complicate the
problems of measurement. USAGE report concluded that open water disposal of contaminated
material is "presumptively" undesirable.
The first CDF in the Great Lakes was constructed at Grassy Island along the Detroit River in
1960, before the environmental impact of contaminated sediments was appreciated. In 1970
Congress passed Public Law 91-611, called the Diked Disposal Program, which provided the
Corps with funds to construct CDFs for storage of polluted dredged materials in the Great
Lakes. The same law provided funds to the Corps' Waterways Experiment Station (WES) to
manage a research program on the environmental effects of dredging and disposal. Today, a
total of about 40 CDFs exist around the perimeter of the Great Lakes on the American side
(EPA, 1990), ai, shown on Figure 3.1. Fourteen are constructed upland using diked or
depressed areas and 26 are built in-lake, either adjacent to the shore or as an island adjacent to
a navigable channel, or harbor, as shown schematically in Figure 1.1. A summary of the
contaminant types, size, age, and location for these facilities is presented in Table 3.1. Several
small and filled CDFs from the Detroit District are not included in this table. Many of the CDF
sediments are categorized as moderately to heavily polluted according to the 1 977 EPA
guidelines presented in Table 2.1. Many of the CDFs are currently being enlargened by raising
the perimeter dikes as the direct result of an inability to site new CDFs.
45
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Table 3.1 Summary Data for Confined Disposal Facilities, U.S. Great Lakes (EPA, 1990)
BUFFALO DISTRICT
1 Cleveland #12
2 Cleveland # 14
3 Dike #4 (Buffalo)
4 Erie
5 Huron
6 Loram
7 Small Boat Harbor (Buffalo)
8 Times Beach (Buffalo)
9 Toledo (Facility 4)
10 Toledo (grassy Is )
CHICAGO DISTRICT
1 Chicago
2 Michigan City
DETROIT DISTRICT
1 Bayport (Green Bay)
2 Bolles
3 Clinton River
4 Crooked River
5 Dickinson Is (Lake St Clair)
6 Erie Pier (Duluth)
7 Frankfort
8 Grassy Is (Detroit R )
9 Harbor Is (Grand Haven)
10 Harsen's Is (Lake St Clair)
11 Kawkawlm River
12 Kenosha
13 Kewaunee
14 Kidney Is (Green Bay)
15 Mamtowoc
16 Milwaukee
17 Monroe (Sterling)
Year
Constructed
1974
1979
1974
1979
1975
1977
196F
1972
1976
1967
1984
1978
1965
1977
1989
1982
1976
1979
1982
1960
1974
1975
1982
1979
1975
1975
1984
Fill Date
1979
1991
1995
1993
1990
1990
1972
1992
1978
1995
1989
1979
1990
....
1992
1990
1993
1990
1984
1985
....
1990
1992
1986
1992
1990
1995
%
Filled
100
40
40
40
70
70
100
45
65
100
10
80
100
25
98
20
48
50
100
100
97
--
-
66
57
97
61
44
-
Capacity
(CD YD)
2,760,000
6,130,000
6,900,000
1 ,600,000
2,150,000
1,850,000
1,500,000
1 ,500,000
10,000,000
5,000,000
1,300,000
50,000
650,000
335,000
370,000
19,500
2,031,000
1,100,000
30,000
4,320,000
310,000
30,000
750,000
500,000
1,200,000
800,000
1 ,600,000
4,200,000
Approximate
Remaining
Capacity
(CU YD)
0
3.678,000
4,140,000
960,000
645,000
555,000
0
Inactive
3,500,000
0
1,170,000
10,000
0
251,000
0
15,000
1,015,000
550,000
0
0
0
Inactive
Inactive
225,000
200,000
0
280,000
800,000
Melais
x
x
x(Hg)
x
X
X
X
X
X
X
x(Hg)
X
x(Hg)
x
X
x(Hg)
X
x(Hg)
x
X
X
x(Hg)
x
X
Volatile Oil &
TKN. AMM. N. COD. P"1 PCBs Oraanics Grease
x
x
X X
X X
X X
X XX
X X
X XX
X XX
X
XX X
X X
X X
X
X
XX X
X X
X X
X
X
XX X
X X
X XXX
X
X XX
X X
46
-------
18 Monroe (Edison)
19 Pionte Mouvile
20 Port Sanilac
21 Riverview (Holland)
22 Sagmaw
23 Sebewamg
24 Verplank (Grand Haven)
25 Whirlpool (St Joseph)
26 Windmill Is (Holland)
(1) TKN = Total Kjeldahl Nitrogen
AMM = Ammonia
N = Nitrogen
COD = Chemical Oxygen Demand
P = Phosphate
Year
Constructed
1979
1979
1978
1978
1979
1974
1978
1977
Fill Date
1984
2009
1983
1993
1990
1989
1977
1987
1988
%
Filled
38
100
48
65
100
75
Capacity
(CU YD)
18,460,000
143,300
120 000
10,000,000
84,000
134,000
25,000
370,000
Approximate
Remaining
Capacity
(CU YD)
Q
11,184,000
0
5,000,000
29,000
Inactive
0
92,000
Metals
y
x(Hg)
x
x
X
X
Volatile
TKN. AMM, N. COD, P1" PCBs Organics
x
x x
x
X X
X
X
X
Oil&
Grease
x
x
x
x
47
-------
Sebewoinq
onilac
Oickensor
Horsen'i
Upland CDF
In-Lake CDF
(EPA, 1990)
Figure 3.1 Locations of Confined Disposal Facilities, U.S. Great Lakes
48
-------
3.1.1 In-LakeCDFs
A summary of the technical specifications and design trends for the 25 in-lake CDFs built by the
USAGE is presented in Table D-1 in Appendix D. Most of the facilities built prior to 1975 consist of
rubble mound dikes with limestone, sand and gravel fill. Such dikes promote free drainage of
effluent during filling, while retaining most solid particles by natural settling and filtration. In some
instances, overflow weirs were installed in the dikes. However, the weirs were not needed or were
ineffective until the sediments clogged the pervious dikes to cut off drainage. The water level is
essentially the same on the lake and fill sides of such pervious dikes: never differing by more than a
few inches. Most of the engineering analyses of such CDFs were concerned with the long-term
stability of the dike during storm wave attack or subsoil settlement.
Since the mid-1970s, there has been increased design emphasis on the use of natural settling and
dike filtration to retain fine particles. As discussed in Section 5, such designs attempt to provide
sufficient effluent retention time to allow for natural gravity settling and/or incorporate natural
aggregate or geotextile filters in the dikes. On some projects, geomembranes and clay/silt layers
were used to line the bottom or sidewalls of a CDF to control flow of effluent through the permeable
filter dike. Many projects have incorporated special filter cells into the dike walls which were
specially designed to remove suspended particles from effluent before being discharged back to the
lake. At the Calumet Harbor facility in Chicago, special sand/carbon filter cells were built on land so
that effluent from the CDF during placement of dredged material could be pumped through the cells
to remove suspended particles and soluble contaminants before discharge into the Calumet River.
The filters were designed to receive influent having suspended solids of 100 ppm and produced
effluent having suspended solids less than 15 ppm.
The capacity and useful life of most in-lake CDFs tend to be large. The capacity varies from the
small 0.12 million cubic yards (MCY) Riverview facility tr, 18.6 MCY facility at Pointe Mouillee with
an average capacity of about 3.5 MCY. The surface area of these facilities varies from 11 to 700
acres with an average of 112 acres. Several of these facilities are filled to capacity and over half are
more then two-thirds filled which suggests that many new facilities will soon be needed.
Fortunately, most of these in-lake facilities have a useful life of more than 15 years except at the
major ports of Buffalo, Cleveland and Green Bay, which were completely filled after several years
because of the frequency and volume of dredging.
3.1.2 Upland CDFs
Technical specifications for 13 of the upland CDFs on the Great Lakes are summarized in Table D-2
in Appendix D. Upland sites are generally selected adjacent to the contaminated area to be
dredged and not far inland because transportation costs are a major factor. Typical sites are either
natural land depressions as at Frankfort Harbor or flat flood plains adjacent to the polluted
waterway. Substrate soils are highly variable and include sand, silt, clay and glacial till. Most sites
need earthen dikes around the perimeter to form the containment area.
49
-------
While most upland CDF dikes were constructed of impermeable clays, several of the diked facilities
were constructed of local soils including silts and sands. Most of these facilities used an
impermeable clay liner on the bottom and sides to inhibit leachate migration. A few, such as the
Whirlpool (St. Joseph) disposal area, used a PVC geomembrane as the liner. Design components
such as clay and geomembrane liners are discussed in greater detail in Section 4.
The polluted dredged materials are placed into the facility by either mechanical (clamshell) or
hydraulic dredging. During hydraulic dredging, the influent pipe is placed at a location remote from
the weir within the CDF to insure that the dredge slurry has sufficient retention time for natural
settling of solids before the effluent passes through the outflow weir. Thus, coarse particles such as
sand, gravel and clay balls are rapidly deposited near the pipe while fine-grained silts and clays
migrate toward the weir and settle. Some fine-grained particles and water-soluble contaminants are
discharged from the CDF. Such point source CDF discharges are frequently monitored to insure
that water quality standards are not exceeded. Oil skimmers can be used to improve effluent water
quality from the CDF when oil and grease are present in the polluted dredged material.
At Michigan City, a sand filter and drain pipes were incorporated into the dike to dewater the
hydraulic dredge material. The filter became clogged during the first dredging operation, rendering
the CDF incompatible with hydraulic dredging. The facility was subsequently filled by mechanical
dredging and trucking since mechanical dredging minimizes the addition of water to dredged
sediment and, thus, the need for a dewatering system. Filter systems are discussed in greater detail
in Section 4.
By comparison, most upland CDFs are very small and have a short useful life, compared to in-lake
facilities. As summarized in Table D-2 in Appendix D, the capacities of the existing unland facilities
vary from 0.020 MCY at Crooked River to 2.0 MCY at Dickinson Island. The average capacity is
only 0.28 MCY for 13 of the upland CDFs around the Great Lakes compared to an average of 3.5
MCY for in-lake facilities. The average surface area is only 36 acres for upland sites compared to
112 acres for in-lake CDFs. Upland sites are politically difficult to locate in populated industrial
areas. At this time 10 of the 14 upland facilities are filled to capacity.
3.2 Sediment Remedial Actions by EPA and States
Since the mid-1970s there has been a concerted effort in Region 5 by EPA and Region 5 states to
remediate contaminated sediments at high priority sites (Elster, 1992) to hasten the goal of
improving water quality in the region. At 20 sites, as summarized in Appendix D on Table D.3,
involving both navigable and non-navigable water bodies, clean-up actions were directed by EPA
and/or the State, using a variety of enforcement authorities and employing a number of remedial
technologies. The EPA has exercised authority under CERCLA, CWA and, to a lesser extent,
through RCRA/TSCA. The states have used the authority provided under the CWA, state
environmental regulations, voluntary agreements with Potentially Responsible Parties (PRPs), and
through Federal grant programs.
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As noted in Table D.3, there have been nine CERCLA and two CWA actions by EPA and nine State
actions dating back to 1977. The effected sediments tend to be heavily contaminated with metals
and organic compounds. The volume of polluted material ranges from a few hundred cubic yards to
tens of thousands of cubic yards. Such volumes are small in comparison to USAGE dredging
projects. The remedial actions usually include:
1) excavation and dewatering of contaminated sediment
2) incineration of heavily contaminated sediments to destroy organic compounds such as
PCBs;
3) placement of contaminated sediments or treated residue in a RCRA type landfill with
appropriate bottom liner and low-permeability caps; or
4) in-situ hydraulic isolation (or containment) of polluted material.
In general, some of the earlier remedial efforts (e.g. Cast Forge Steel in Howell, Michigan) were
ineffective because of poor containment design and were often left incomplete because of cost
overruns (Elster, 1992). Recent remediations tend to be more successful because they emphasize
in-situ containment with dredging and treatment of contaminant hot spots. For instance, sediments
from the contaminant hot spot at the Outboard Marine Corp. site in Waukegan, IL were dredged and
thermally treated to remove the PCBs. Peripheral contaminated sediments (<500 ppm) were
dredged, dewatered, and placed in a hydraulically isolated waste disposal cell on site. The treated
hot spot sediments were placed over the isolated peripheral sediments and were in turn covered
with a low permsaNity cap.
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SECTION 4
DESIGN AND PERFORMANCE OF EXISTING CDFs
This section compares recent in-iake and upland CDF projects by the USAGE to EPA/State
sediment remediation projects. All projects referenced are within EPA Region 5. As discussed in
Section 2, the CDFs are designed to handle dredged materials that can contain a high volume of
free water. The CDFs are designed to ensure that effluent coming from within the CDF will not
cause levels of contamination in adjacent surface waters that exceed the CWA established MCLs
and State water quality standards (WQS). The effluent can be treated, filtered, or allowed to dilute
within a defined mixing zone. TSCA and RCRA disposal facilities are, however, primarily designed
for waste streams that have no free water. These disposal facilities must provide maximum possible
isolation of the waste from proximal ground and surface waters.
The significant quantity of free water associated with dredged material disposal provides for design
complexities not common to PCB or hazardous waste landfill designs. Such considerations include
evaluating the potential for contaminant solubility in the effluent waters, the level of contamination
bound to dredged material solids, the impact of sediment dredging, handling, and disposal
operations on contaminant migration potentials at the CDF, and sediment or effluent treatment
alternatives if the effluent within the mixing zone does not satisfy CWA or State WQS.
4.1 USAGE Projects
The design and construction of in-lake and upland CDFs has evolved during the past 25 years to
include new technologies and updated environmental criteria. Many of the CDF design details are
site- and facility-specific, and require a detailed evaluation of prospective site conditions. The Corps
has frequently published guidance documents during this period as part of the Dredged Material
Research Program DMRP (1973-1978) and several other programs to deal with specific problems
such as dewatering/densifying (USAGE, 1978), disposal area reuse (USAGE, 1978a) and
estimating the quality of effluent from a CDF (Palermo, 1986). These and other documents have
evolved into a manual entitled "Confined Disposal of Dredged Material" (USAGE, 1987a) which
conveys the state of the art in design, operation and management of CDFs.
4.1.1 CDF Design Criteria/Objectives
At the present time the USAGE CDF Manual (USAGE, 1987a) emphasizes two primary objectives
associated with the design of in-lake and upland CDFs to store contaminated sediments:
1) Maximize Retention of Fine Particles. The Dredged Material Research Program has
shown that most contaminants are adsorbed to the surface of the finer soil particles
such as silts and clays. The sediment pore fluid is significantly less contaminated
and is diluted during dredging and upon release from the CDFs as an effluent.
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2) Maximize Storage Capacity/Useful Life. The economics of dredged material
disposal includes the administrative process by which most CDFs on the Great
Lakes were planned and constructed. This process presently takes about 10 or
more years, which dictates the minimum capacity/useful life of a CDF be at least 15
to 20 years.
From an engineering perspective, existing CDFs are designed as wastewater treatment facilities
where the objective is to capture particles with adsorbed contaminants. These CDFs assume the
partitioning potential of the contaminants is minor or moderate as previously detailed on Table 1.2.
Effluents and other discharges are regulated by the CWA, as noted in Section 1, and must satisfy
State WQS. Therefore, the sediment basin and weir are designed and operated to promote gravity
settling of solids. According to the USAGE CDF Manual, the settling process will normally remove
suspended particles down to a level 1 to 2 g/l in the effluent for freshwater conditions. This is about
99% efficient when considering a typical CDF influent of 100 g/l. If water quality standards are not
met by gravity settling, the designer must provide for additional treatment of the effluent by
flocculation or filtration or use a mixing zone or zone of dilution in the receiving waters. Filters have
been included into the design of several CDFs as noted in Tables D-1 and D-2. However, the
effective operation of a filter is often short-lived because fine particles quickly plug the pores of a
filter and cut off flow unless the filter face is cleaned periodically. The size of a potential mixing-
zone depends upon a number of factors including the effluent contaminant concentration,
concentrations in the receiving water, the applicable water quality standards, effluent density and
flow rate, receiving water flow rate and turbulence, and the geometry of the discharge structure and
receiving water boundaries. The evaluation of mixing-zone geometry is based on calculation of
near-field dilution and dispersion processes which can be performed using the available computer
models that yield order-of-magnitude estimates (see Inland Testing Manua's 1993). While
computational methods provide an excellent estimate of dispersion, a dye plume study at the
proposed discharge site is considered to be the best method of evaluating mixing zone dimensions
although it is costly and time consuming. Also, many state regulatory agencies specify limits on the
dimensions of the mixing zone that can be incorporated into a CDF design, thus limiting the mixing
zone as a design element.
From a structural perspective, CDFs are generally created by constructing dikes around the
perimeter of the site with the goal of creating stable, long-term containment of dredged material.
Upland facilities typically have compacted low-permeability earth dikes, whereas most inlake CDFs
have permeable stone dikes that are constructed with layers of stone of increasing size over a core
of sand and gravel. In-lake CDFs with stone dikes are generally permeable when first constructed
but become progressively less permeable due to clogging during filling operations. Variations to
these basic dike structural designs have included the use of sheetpiles and liners, such as clay
layers and plastic membranes, for improved structural or hydraulic performance.
Several examples of in-lake and upland CDFs are presented in the following sections to illustrate
the design features used to contain polluted dredged materials compared to RCRA/TSCA approved
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hazardous/toxic and solid waste disposal facilities. For contaminants having a high partitioning
potential (reference Table 1.2), the trend in CDF design has been away from the solids retention
approach and towards the hydraulic isolation of "dewatered" sediments through the use of natural
and synthetic impermeable liners and caps to control the release of pollutants through the base and
dikes of the CDF. Such hydraulic contaminant CDFs force the effluent to exit the CDF through a
point source. This allows the potential for better control, treatment, and monitoring of effluents.
Because of the limited availability of land for siting CDFs in populated areas and public concern for
the environment, the last in-lake CDF was built at Monroe Harbor, Michigan in 1983 and the last
upland CDF at Clinton River in 1989.
4.1.2 Example of In-Lake CDFs
Buffalo/Lackawanna - Dike #4 An early example of a rubble mound in-lake CDF is the
Buffalo/Lackawanna Dike #4 which was constructed in 1974 at the south end of Buffalo Harbor
(Figure 4-1V This facility was used to contain dredged materials from Buffalo and Dunkirk Harbors
which were heavily contaminated with several metals including mercury, plus oil, grease and PAH's.
The outer walls of the CDF are in 30 feet deep water depths, and exposed to large wind induced
currents and wave forces. Rubble mound construction is an economical solution for this harsh
environment and costs were reduced by incorporating the adjacent coast line and an existing
sheetpile breakwater into the containment structure.
A typical design section of the rubble mound structure is shown in Figure 4-2 which reveals the
various zones of granular fill, armor stone and 5-foot thick filter blanket that abuts the dredged
material Because the subsoil is a soft lake clay to sandy silt, 50-foot wide berms were added to
each side of the main dike to improve the support capacity of the soft subsoil and prevent instability
of the dike.
Contaminated sediments are dredged using both hydraulic and mechanical methods. When placed
in the CDF, the dredged material is dewatered by natural settling. Solids in the effluent are
minimized given an adequate residence time before the effluent is discharged through a single weir
located along the existing sheetpile breakwater. Placement of dredged materials within the CDF
has not yet risen to a levei where the weir is used. In addition, dredging fluids are filtered at the
inside face of the dike by the natural aggregate filter. However, there is considerable uncertainty
about the efficiency of this filter because of the hydraulic construction techniques.
There are no monitoring wells in the dike to evaluate effluent quality and water quality is not
monitored at the weir since no effluent has yet risen to the level of the weir. Monitoring outside of
the CDF has shown no degradation of background water quality. This CDF should be filled to
capacity by 2015. While there are currently no plans to cap the facility, the ultimate intended use is
as a wildlife area.
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A
N
SCALE IN FEET
500 1000 1500
(EPA/905/9-90/003)
Figure 4.1 Dike Disposal Area for Harbor Dredging - Buffalo, New York
55
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568 6
553.6
538.6 B/L
is
HARBOR
582 6T/S
1.5 ^_X-
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LAKE
(BW)
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10 5'-9-13 Ton Stone
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i
0
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IS
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SECTION A-A
(£ PA/905/9-90/003)
Figure 4.2 Typical Dike Section - Buffalo, New York
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Kidney Island CDF, Green Bay Harbor, Wl The Kidney Island CDF is a 60 acre facility built
during 1979 about 800 feet offshore in about 10± feet of water (Figure 4-3). It was designed to
accept dredged materials from the Fox River and Green Bay Channels which are excavated using
either hydraulic or mechanical methods. The dredged materials are polluted with metals such as
mercury, arsenic and chromium, in addition to PCBs and volatile organic compounds.
The dike design consisted of a core of limestone rubble as shown in Figure 4-4. A 72 mil plastic
liner was originally planned to contain the fine grained dredged materials but was apparently
abandoned during construction. Ideally, the plastic liner would force effluents through a filter cell
which was constructed of sheet piles driven within the dike wall (Figure 4-5). However, without the
membrane, flow through the permeable dike walls would eliminate discharge through the weir/filter
cell until the dike walls become plugged with dredged materials. The CDF as constructed did not
incorporate the plastic liner but did use sheet piles with asphalt interlocks as a cutoff wall to limit
effluent discharge through the dikes. The limestone core was also felt to be significant in limiting the
movement of metals through the dikes.
There has been some monitoring of water quality during and after dredging operations. This was
achieved by sampling fluids at the dredge pipe influent discharge, inside of the filter cell, within the
mixing zone outside of the weir, at an open water site, and at three monitoring wells - two in-dike
and one in-filter. This CDF is about filled to capacity and is intended to remain a wildlife habitat.
Some special biological studies have been performed at this site including bird nesting activities and
a plant survey.
Chicago Area CDF, Calumet Harbor, IL The Chicago Area CDF was constructed in 1982 to
contain heavily polluted dredged materials from the Calumet River and Harbor and the Chicago
River and Harbor. This 40 acre facility is located within Calumet Harbor adjacent to the Illinois
International Port Authority's Iroquois Landing development (Figure 4-6). The Chicago CDF
represents the first of the "hydraulic barrier" CDFs designed for problematic dredged materials under
the regulatory scenario shown on Table 1.2.
As with other in-lake facilities, this CDF is comprised of a prepared limestone core and is covered by
a protective armor stone as shown in Figure 4-7. The particle size distribution of the prepared
limestone has 100% of the particles smaller than 61/2 inches and virtually no fines passing the 200
sieve. This gradation creates a highly permeable core through which water and fine particles could
migrate freely. To minimize migration of contaminated fines and effluent through the limestone core,
the original design included an impervious membrane placed on the inside surface of dike and a
filter cloth on the lake side surface of the dikes core as part of the dike's aggregate filter. The filter
cloth was omitted during the final design, although its inclusion was suggested in the EIS. Armour
stone was to be placed over the membrane and filter cloth. Consequently, there was damage to the
membrane during installation and a dye study was performed to evaluate the extent of damage.
The dye study showed that discharge from the CDF was occurring so a layer of fine sand was
placed along the inside face of the dike to restrict the movement of fines through the dike.
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Trmirt^b
r*l*l« 43
formerly
Confined '
. Disposal Area
'/^trr.-/,^,^
//X-iV It-- ^ ;
QUEEN BAY HARBOR. WISCONSIN
(liPA/905/9-90/003)
BAYPORT CONFINED
DISPOSAL AREA
Figure 4.3 Bayport Confined Disposal Area - Green Bay Harbor, Wisconsin
58
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INTERIOR OF CDF
COVERSTONE 35-100 IbS
2 LAYERS RANDOMLY
PLACED-i 6' THICK
BOTTOM 7-11' 6ELOW,
L.WO REMOVE SOIL
AS NECESSARY
LAKESIDE
CREST (g 15'
PREPARED
LIMESTONE CORE
COVERSTONE
2 LAYERS RANDOMLY
PLACED -4.C/ THICK
It Mil SOLID
PLASTIC LINER
UNDCRLAYtR,
£ LAYERS RANDOMLY
PLACED-Z I'THICK
(EPA/905/9-90/003)
NORTH AND EAST DIKE SECTION
GREEN DAY HARBOR
CONFINED DISPOSAL FACILITY
OFFSHORE ISLAND CDF
KIIINKY ISLAND I 111
Figure 4.4 Typical Dike Section - Green Bay Harbor, Wisconsin
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L
AM
P/L£ w i r M
ASPHALT
-17
KIDNEY ISLAND LiJh
(EPA/905/9-90/003)
Figure 4.5 Efflent Filter and Outlet Structure - Green Bay Harbor
60
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VEIL
a
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Figure 4.6 Siteplan of Chicago Confined Disposal Facility
61
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ramu* tmtmm
CftADATION
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4" 001-lOOt
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J/4" 211- 111
)/»" IM- 4M
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CIIICACO CONI INI-.O DISPOSAL IACII.ITY
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JAMIADI l«ll
(EPA/905/9-90/003)
Figure 4.7 Typical Dike Section - Chicago CDF
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During the filling operation and following primary settling, all effluent flowed to a secondary
settlement basin from which it was pumped to two large sand/charcoal filters for additional filtration
before release to the Calumet River. Pumping from the CDF creates a negative hydraulic gradient
in the dike and limits flow out of the CDF during dredging operations. The pumping is stopped
following placement of dredged material.
There has been an extensive water quality monitoring program at the CDF and a number of special
studies. During disposal operations, water quality samples are obtained from 5 stations in the
Calumet River and Harbor and filter cell influent and effluent. In addition, monthly samples are
taken from the 9 monitoring wells around the CDF as shown in Figure 4-6. Special studies have
included dye tests during construction to determine liner integrity, field observation of wildlife and
PCB body burdens of CDF fish and benthos.
This CDF will be filled after the year 2000 and will be capped by a 2-foot layer of clay plus one foot
of topsoil and cover.
4.1.3 Examples of Upland CDFs
Dickenson Island CDF, Clay Township, Ml The largest upland CDF in the Great Lakes is the
Dickenson Island facility with an area of 174 acres and a capacity of 2 million cubic yards. It was
built in 1976 on two sites at the north end of the island to accommodate dredged material from the
channels in the St. Clair River delta at Lake St. Clair (Figure 4.8). The sediments are heavily
polluted with the metals, mercury, lead and arsenic, plus nutrients and were placed in the CDF using
hydraulic and mechanical dredging methods.
This CDF was created by building an earthen clay dike around the perimeter of each site as shown
schematically in Figure 4-9. A weir structure was built into the dike to return clarified effluents back
to the North Channel after natural settling was used to separate the sediment fraction from the water
fraction. The site is underlain by a substrate of permeable silty sand. When this CDF is filled to
capacity in the late 1990s, the site will be acquired by the State of Michigan for incorporation into the
St. Clair Flats Wildlife Area. There are currently no plans to construct a final protective cover (clay
cap) over the facility.
There has been some monitoring of water quality by the USAGE during and after dredging using
samples acquired at the dredge pipe influent discharge, weir overflow and within the mixing zone
upstream and downstream of the weir discharge, and from monitoring wells in the dike. The
USAGE (1982) study concludes that "there is no significant alteration of ambient stream water
detected during the two sampling events." and "No leaching through the dike wall was observed
or detected from the well samples." Yet "the well samples had consistently higher lead
concentrations as compared with dredge discharge water, weir, plume and stream samples." No
special studies, such as biological testing, were performed at the site.
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DICKINSON
ISLAND
Figure 4.8 Site Plan of St. Clair Disposal Area - Dickenson Island, Ml
64
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PIIUI'-Olll UCII I I US
OlSOlARU PIPI
ORAIN I0f<
'UCfSS IfflUINI
IROU DKIIH.I
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Sellloenl Basin
J:
WEIR STRUCTURE
DICKENSON ISLAND CDF
Figure 4.9 Wier Structure - Dickenson Island, Ml
(EPA/905/9-90/003)
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Sebewaing Disposal Area, Ml The Sebewaing, Michigan disposal area was constructed in
1979 adjacent to the Sebewaing River (Figure 4.10) just upstream from Lake Huron. This is a small
facility with an area of 9 acres, capacity of 84,000 cubic yards, and a rectangular shape. It was
designed to contain slightly contaminated dredged materials from the Sebewaing River and Harbor
where the primary pollutants are nutrients derived from agricultural runoff.
This facility was constructed by placing a 7-foot high clay dike around the perimeter of the site.
Typical dike sections are presented in Figure 4-11 which show the low dike geometry and a surface
armoring of rip rap and filter cloth on the outside of the west dike to prevent storm flood damage
from Lake Huron. In 1987 repairs were needed to the west and north dike walls. The dikes were
built on a substrate consisting of a thin layer of organic wetland soils on top of glacial till. The
combination of impermeable substrate and clay dike create a very effective containment structure
for polluted sediments since little or no leachate would be released. Dredging effluents were
subjected to natural settling to remove solids before discharge over a weir to the Sebewaing River.
Water quality data were obtained at the weir and in the mixing zone during placement of dredged
sediments from maintenance dredging operations at the navigational channel at Sebewaing Harbor
(USAGE, 1988). The water in the mixing zone was light brown and could be easily delineated from
normal background. Suspended solids in the overflow were as high as 94 mg/l (94 ppm) and 38
mg/l in the mixing zone. Water quality data indicated elevated total Kjeldahl nitrogen (TKN)
concentrations at the weir (28 mg/l) and within the mixing zone (17 mg/l) compared to upstream river
concentrations (0.87 mg/l). Similarly, chemical oxygen demand (COD) concentrations at the weir
and within the mixing zone were elevated compared to upstream concentrations. The CDF
discharge caused slight increases in TKN, COD, and ammonia nitrogen levels in the mixing zone
but had little impact on downstream river concentrations. The report concludes that "There was
minimal impact on water quality in the Sebewaing River." When filled, this facility will be acquired by
the State of Michigan to extend the Sebewaing County Airport with portions user! as a wildlife
habitat.
Michigan City CDF, IN The Michigan City CDF is the smallest CDF constructed to date at only
3.3 acres. It was constructed in 1978 on the edge of the Trail Creek about 1.5 miles upstream from
Lake Michigan. The facility contains 50,000 cubic yards of sediments that are contaminated with
metals such as arsenic, cadmium and chromium, in addition to PCBs and oil and grease that were
discharged by a nearby wastewater treatment plant and local industry into Trail Creek.
The dike was constructed of compacted earth with the substrate consisting of a silty sand over clay
which acts as a lower impervious liner. The outside of the dike along the creek has a stone rip-rap
surface for erosion protection. The facility includes a sand filter in the dike to supplement the
primary settling of effluent. Hydraulic dredging was first used to fill the facility but the filters became
clogged. This necessitated a change to mechanical dredging and trucking to complete the filling.
This site has been filled to capacity and capped with 2 feet of clay and 2 feet of top soil.
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SEBEWAING DISPOSAL AREA
SEBEWAING,MICHIGAN
ENLARGED SITE PLAN
(EPA/905/9-90/003)
Figure 4.10 Site Plan of Sebewaing Disposal Area
67
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DIK.6
i /-\M
tO'-O
TO P. EL.
>H7TLlM£NT
SOUT-i
DIKE SECTIONS
SEBEWAING DISPOSAL AREA
SEBEWAING, MICHIGAN
(EPA/905/9-90/003)
Figure 4.11 Typical Dike Section - Sebewaing Disposal Area
-------
There has been a considerable monitoring effort at this site. This has included sediment grab
samples and surface water samples during dredging and disposal. Borings were also made in the
dike after clogging to evaluate contaminant migration. Groundwater was monitored before the last
disposal operation and for one year following on a quarterly basis from three wells, 1 upgradient and
2 downgradient of the CDF. These results showed that the groundwater between the CDF and Trail
Creek had higher levels of ammonia-nitrogen and metals iron, manganese, and barium than the
upgradient well.
4.2 EPA/State Remediation Projects
4.2.1 Sediment Remediation Criteria/Objectives
The remediation of contaminated sediment sites by the EPA and regional States is primarily
concerned with the improvement of water quality (both groundwater and overlying surface water)
and a reduction in contaminant loads to the lakes and the potential long-term impacts on aquatic
biota and human beings. Since most in-situ sediment pollutants are adsorbed to the surface of
sediment particles, contaminated sediments can continue to act as a pollutant source and degrade
water quality long after point and non-point sources are eliminated. Contaminant release continues
to occur as a result of polluted sediment erosion during storms, sediment stir-up by vessels and
biota, groundwater flow through the polluted sediment and, to a lesser degree, from diffusion of
pollutants off sediment to the overlying water. As discussed in Section 1, the EPA and States have
been given the authority to implement contaminated sediment remedial activities from a number of
legislative acts.
Superfund (CERCLA/SARA) provides funding and th*3 authority to remediate inactive or abandoned
hazardous waste sites that pose a hazard to human health and the environment. The major
objective of Superfund is to recover, treat or destroy pollutants to the degree dictated by economics
and to hydraulically isolate wastes and contaminated environmental media. Hydraulic isolation can
be achieved by either constructing barriers in-situ or by excavation and placement of polluted
sediments in approved disposal facilities.
Sediment remediation authorities are also provided under RCRA-C. These authorities apply to
sediments that were contaminated as the result of the release of hazardous waste or hazardous
constituents from a solid waste management unit (SWMU) located at a RCRA-C facility. A RCRA-C
facility is defined as a facility authorized to treat, store, or dispose of hazardous waste as defined
under 40 CFR 261.
An important factor in the Agency's decision to remediate a fresh-water site is the environmental
impact of the dredging excavation process with its resuspension of particles and potential further
spread of pollutants. Where an unacceptable adverse dredging impact is anticipated, a decision of
"no removal action" usually termed the "no action alternative" may be considered as the solution. At
low energy sites where resuspension of contaminated sediments is not a problem, a decision of "no
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removal action" may also be chosen to allow natural sedimentation or the placement of an artificially
cover consisting of clean sediment upon the polluted materials. Because of the potential for risks
associated with a remedial action to excavate and treat a polluted sediment, the "no removal action"
decision is currently preferred over the other alternatives when site conditions mitigate against
removal. Table 1-2 indicates that on-site disposal has been the preferred remediation alternative in
Region 5. This was in part due to the high liquids content of the sediments and the difficulties
associated with the transport of such large volumes. The decision to remediate a fresh-water site by
dredge excavation and placement of the sediments in a CDF facility or through treatment requires
special planning and precautions to minimize the resuspension and spreading of pollutants.
4.2.2 Example Remediation Projects
OMC/Waukegan Harbor Superfund SiteThe Outboard Marine Corporation (OMC)/Waukegan
Harbor, Illinois Superfund site provides an example of a PCB contaminated sediment remediation
involving the recovery and incineration of PCBs and hydraulic isolation of additional polluted
sediments.
From about 1960 to 1975, the OMC purchased hydraulic fluids containing PCBs for use in die-
casting operations. During plant operation and maintenance, large quantities of PCBs escaped into
adjacent Waukegan Harbor and onto OMC property (Figure 4.12A). The EPA estimates that over
one million pounds of PCBs were left at the site including about 700,000 pounds remaining on the
north side of OMC property and about 300,000 pounds to slip 3 and Waukegan Harbor. Some of
the PCBs are known to have affected water quality in Lake Michigan.
Following a long study of the site and protracted litigation between EPA and OMC, the remediation
design and construction was started in the late 1980's. The remediation included the construction of
three slurry wall containment cells around the PCB hotspots: one in Slip 3, and two in the north
portion of the site. Each slurry wall penetrates into the underlying clay till and is three feet thick. At
the mouth of Slip 3 (Figure 4.12B) a double sheetpile cut-off wall with clay slurry fill is used to isolate
Slip 3 from the Upper Harbor. Hotspot sediments from Slip 3 (>500 ppm) and the other two sites
(>10,000 ppm) were excavated and treated on site by a low temperature extraction procedure to
remove at least 97% of the PCBs by mass. The recovered PCBs were removed to a TSCA
approved facility for destruction. Residual treated sediments and soils were returned to the
respective containment cells. In the Upper Harbor, sediments with PCB concentrations between 50
and 500 ppm were hydraulically dredged and placed in the Slip 3 containment cell. Each of the
containment cells is to be capped with a clay layer and have extraction wells installed to prevent
PCB migration from the cells. All water generated at the site is treated by filtration to further remove
PCBs before discharge.
Deer Lake, MichiganThe Deer Lake remedial effort is interesting from the perspective of a "low-
action" alternative. The 906 acre impoundment is located in Michigan's Upper Peninsula and is
connected to Lake Superior by the Carp River. Iron mining is the major industry in the area but
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Figure 12A Site Location of OMC/Waukegan Harbor Superfund Site
Cleanup of
OMC/Waukegan
Harbor
Superfund
Site
Figure 4.12B Site Plan of OMCAA/aukegan Harbor Superfund Site
71
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the lake's drainage basin. Mercury was detected in fish at levels exceeding the FDA action level of
1.0 pprn wet weight and the state of Michigan consumption advisory level of 0.5 ppm. This lead to
fish consumption and health advisories in 1981 which are still in effect. Lake sediment hot spots
contain mercury in concentrations up to 10-15 ppm. The major source of pollution was the
Cleveland Cliffs Iron Company (CCI) laboratories which used mercuric chloride for its ore assays
and research. Mercury discharges were passed to Deer Lake by CCI via the Ishpeming, Michigan
Wastewater Treatment Plant and Carp Creek. Disposal of mercury was curtailed in 1981 when the
source was identified.
In the fall 1984, the Michigan Department of Natural Resources (MDNR) and CCI signed a consent
degree which outlined a restoration and monitoring plan for Deer Lake with financial responsibility
assigned to CCI. The primary goal of the plan was to create an uncontaminated fishery over a 10
year period. This was to be achieved by allowing natural sedimentation to bury the contaminated
sediment to eliminate their mobility. The plan initially required lowering the lake to eradicate the
contaminated fish. The fish were first netted and the remainder subsequently treated with rotenone
to kill about 90% of the population. To prevent downstream transport of rotenone, a diversion trench
for Carp Creek was excavated around the lake. In the spring 1987, the lake level was restored to
the top of the dam where it will remain until 1997. Fish were stocked in the lake. A 10-year
monitoring program requires periodic sampling and testing offish, sediment, water and ice that
formed over impacted tailing piles. While mercury levels in the fish only allow for catch-and-release
fishing, the mercury levels in surficial sediments has dropped from a high of 15 ppm to about 8.3
ppm in 1991 (Elster, 1992) which appears to be a small improvement. Yet, at the end of the 10 year
monitoring period, the mercury levels in the fish are expected to be comparable to other lakes in the
area. There are no price data on this restoration project but it is undoubtedly a "low-cost" effort
compared to the alternative of excavation followed by treatment and landfilling.
PR Mallory - Crawfordsville, IndianaThe EPA remediation (CERCLA/SARA) of the PR Mallory
site in Crawfordsville, Indiana represents a "classic" example of the EPA approach to hydraulic
isolation of contaminated waste and environmental media, in this case, sediments. The PR Mallory
facility manufactured capacitors from 1957 to 1969 but the facility was abandoned in 1970 after total
destruction by fire. The company was later acquired by Duracell International, Inc. In 1985 the
Indiana Department of Environmental Management investigated the site and found capacitors in a
ravine that leads to a creek. The capacitors contained oil with PCB concentrations up to 100%. A
subsequent EPA site investigation found PCB concentrations up to 165,402 ppm in the soil and up
to 9,695 ppm in the ravine sediments. EPA issued a CERCLA Administrative Order to Duracell and
the current owners and Duracell agreed to preform the specified remediation.
The Order specified removing all the contaminated soil and ravine sediments above 25 ppm PCBs
and placement in a hazardous waste landfill. An extensive sampling and testing program was
initiated to determine the areas requiring excavation. During excavation, contaminant migration
through the ravine was controlled by a series of sediment traps and oil-absorbent booms across the
stream. The ravine sediments were dewatered and stabilized in place prior to excavation and
72
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placed in an interim storage facility. Upon completion of the excavation, the sediment traps and oil
booms were removed and added to the interim storage facility. The ravine was regraded with clean
fill to promote drainage and revegetated.
The final phases of the remediation included excavation of contaminated soil beneath the
manufacturing building and placement of all contaminated soils and sediments in the TSCA landfill
in Emelle, Alabama. As of June 1990, 60,000 c.y. of contaminated material had been processed
(Elster, 1992) at a cost of $28 million or $460/c.y. More excavation is needed beneath the facility.
Monitoring of the ravine and downstream creeks will continue for several years.
73
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SECTION 5
CONTAMINANT PATHWAY CONTROL
Contaminants from sediments contained within a CDF can be discharged to the environment via the
six potential pathways discussed in this document. These pathways are shown on Figures 1.3 and
5.1 and include three water borne pathways (1,2,3) the direct uptake of the contaminant by plants or
animals (4,5) and air borne emission of contaminants (6). With the addition of the air borne
emission pathway, these pathways are consistent with the five potential contaminant pathways
identified in the USAGE technical framework (EPA/USACE, 1992) discussed in Section 2.1 and
shown on Figure 2.2.
5.1 Water Borne Contaminants
The control of water borne contaminants must consider both the contaminants dissolved in the
effluent and the solid contaminant fraction associated by adsorption or ion exchange with the total
suspended solids (TSS) within the effluent (Thackston and Palermo, 1990). Given sufficient
retention time in a containment area, non-colloidal suspended solids will settle out of the effluent
and be retained. This designed practice of "solids retention" is the basis for the USAGE design
process but may be limited by either high contaminant concentrations or partitioning, see Table 1.2.
A "hydraulic isolation" design criteria for the CDF is assumed when high contaminant concentrations
or partitioning threaten release of excessive contaminants to the environment. It is also anticipated
that effluent treatment would be required under these circumstances.
The suspended solids concentration in effluent water is influenced by the pond surface area and
residence time for the effluent within the CDF. The conventional USAGE design procedure
determines the design surface area or the residence time required for sedimentation to meet effluent
suspended solids requirements. Both design calculations assume that the CDF dikes are
impermeable to the effluent and that the dredged material was hydraulically dredged or disposed.
The procedure for calculating the minimum required surface area, shown on Figure 5.2, recognizes
that sediments fall out of suspension quicker in ponds having larger surface areas and shallow
depths. The reason for this is that, in deep ponds, the falling sediment particles begin to collide and
creates what is termed compression settling. Compression settling is very slow compared to normal
settling rates of soil particles and therefore results in an increase in the required retention time. The
minimum required surface area for the pond is calculated in two ways: (1) based on the storage
volume required for the dredged material once it settles out of suspension, and (2) based on the
settling time required for the sediments to fall out of suspension. The larger of the two areas is then
assumed to be the minimum required surface area for the pond within the CDF.
Having solved for the minimum pond area in the previous paragraph, the USAGE procedure then
calculates the minimum residence time for the supernatant within the pond as shown on Figure 5.3.
A percent solids removal verses time relationship is first established based on the pond depth and a
74
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Contaminants in
Dredge Materials
Section 5.3
Volatilization of
Contaminants to
the Atmosphere
Section 5.1.4
Surface Runoff
Caused By
Precipitation
Direct Ingestion
of Contaminants
Section 5.2.1 Plants
Section 5.2.2 Animals
Human Uptake
Section 6.3
Animal Uptake
Figure 5.1 Transport Mechanisms of Contaminants to Environment
75
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Compute Volume of
Fine Grained Sediments
After Disposal
Log of nrne, T
ompute Deeign Solids Concentrator
Estimate Volume of Dredged Material
Maximum height material can be placed
-maximum allowable dike height due to
foundation conditions
-ponding depth
-freeboard (mkiimum 2 teet)
|_ -length of contahmont coll
w -width of containment crt
Surface Area for Flocculent Sedimentation
Surface Area for Storage Volume
Figure 5.2
COE Design Procedure for Determining the Design Surface Area Required
for Sedimentation to Meet Effluent Suspended Solids Requirement
76
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r
~i
0 r. Dry Weight of '<»
Initial Concentration
Construct Time Versus % Solids Removol Curve
Required Solids Removal
= Q -C.H
Q
Initial Suspended Solids
C,
0
1 '
I2
0 X Dry Weight of
Initial Concentration
10°
Compute Solids Removal
sn.-^Lx too
An
-I Increase lime
Pond Depth = HM ,
X Solids Removal
(SR)
Correct Td for
Hydraulic Efficiency
t length of containment cell
w - width of containment cell
-CD
Figure 5.3 COE Design Procedure for Determining Residence Time (T)
Required for Sedimentation to Meet Effluent Suspended Solids Requirement
77
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range of assumed times. Knowing the suspended solids requirement for the effluent, the residence
time (Td) based on pond depth is established. The actual design residence time (T) isobtained by
modifying Td based on the actual length and width of the pond.
Within this section, the water borne contaminant pathways are discussed independently. This
discussion reflects the differences in release mechanisms and associated design of pathway control
devices.
5.1.1 Effluent Flow Through Weirs and Filters
Pathway controls for contamination related to TSS in effluent leaving the CDF through a weir are
charted on Figure 5.4. Current USAGE weir design procedures focus on the removal of suspended
solids from the effluent. This assumes than significant partitioning of the contaminants to the water
will not occur, see Table 1.2. Four design alternative courses of action for the control of suspended
solids in the effluent are charted on Figures 5.5 (Krizek, et al, 1976). Pervious dikes are
recommended by the USAGE to filter effluents with concentrations of suspended solids up to 0.5
gm/l (Case 1). Such dike filters constitute a low maintenance filter that is characterized by very
large filter depths and long effective lifetimes. For cases where the influents are expected to have
suspended solids concentrations up to 1 to 2 gm/l, the sandfill weir offers an attractive alternative
(Case 2 and 3). Sandfill weirs designed without backwash capabilities require maintenance to
replace clogged filter media at periods significantly shorter than pervious dike lifetimes. Although
the type of influent to be treated with the sandfill weir is similar to that for pervious dikes, its mode of
operation is much more flexible.
Granular media cartndoes can be used with waters having loads of suspended solids loads up to 10
gm/l (Case 3); however, maintenance requirements are expected to be excessive at loads higher
than a few grams per liter. Typical filter systems include pervious dikes (Figure 5.6), and
downflow/upflow weirs or cartridges (Figure 5.7). The pervious dikes are designed to filter out the
suspended solids by selecting the filter media particle size distribution using conventional
geotechnical filter criteria. Clogging of the pervious dike is minimized by using stratified or baffled
dike sections that provide a control over the maximum flow gradients that develop within the dike
section. The larger the potential flow gradient; the smaller the potential for clogging of the filter. The
filter weirs and cartridges shown on Figure 5.7 function similar to the filter dikes. Such systems
allow the designer to maximize the removal of suspended solids and minimize the potential for
system clogging.
The suspended solids concentration in effluent can be significantly influenced by the length of the
weir (sharp crested, rectangular or shaft type) and the depth of the pond as shown on Figure 5.8.
Water borne suspended solids and the associated contaminants that cannot be removed by basin or
weir design, may render the effluents from disposal areas unacceptable for discharge to open
waters and it may be necessary to employ a filter system or chemical methods (Schroeder, 1983) to
clarify disposal area supernatants.
78
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Fluid Migration of
Suspended Solids
Transport of
Dissolved Contaminants
Unrestricted
-* No Attenuation
Coarse Granular
Material with
Little or no Fines
Coarse Granular
Non-Reactive
Material with
Little or no Fines
j Appendix A - Section 4
I
I
Bioreclamation
and Bioreactors
Chemical -
chelation, nucleophillic
substitution, oxidation
of organics
Extraction/
Adsorption
Figure 5.4 Control of Contaminant Pathway Through Weir
79
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Characteriatici of Disposal Area
Amount and
Gradation of
Suspended Solids
la Slurry
Surface Area
Flow fuite
Surface Loading
Required
Effluent
Quality
(B)
Concentration of Suspended
Solids in Effluent (A)
Effluent Quality
(coapare A and B)
Acceptable
A £ B
Not Acceptable
A > B
No Need for
Further Treacaent
Treatment Required
C - A - B
Case 1
C < 0.5 g/Z
Case 2
0.5g/l 10 g/i
(Ref. Krizeketal, 1976)
Figure 5.5 Flow Diagram of Alternative Courses of Actionto Evaluate
Effect of Sedimentation of Disposal Area Effluents
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Protective Layer |$g^ Fillef Medium
Sh3 Coarse Gravel
Foundation Soil
Impervious Material
Fine Grovel
(a) Homogeneous Sectior
(b) Stratified Section
(c) Baffled Section
(after Krizek, et al. ,1976)
Figure 5.6 Pervious Dike Filter Systems
81
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Filter Medium
Graded Gravel
Coarse Stone
Foundation Soil
/ \
(a) Oownflow Weir
(c) Down flow Cartridge
(b) Upflow Weir
(d) Up Mow Cartridge
Figure 5.7 Filter Weirs and Cartridges
(after Krizeketal., 1976)
82
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ZONE OR
COMPRESSION
SETTLING
0.5
wcm LOADING, an.
(Ref. EM 1110-2-5027)
Figure 5.8 Weir Design Nomograph
83
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The removal of dissolved contaminants from effluent leaving the weir is performed using treatment
technologies that are very contaminant specific. A general discussion of these technologies is
presented in Appendix A.4.
5.1.2 Dike Seepage
Movement of contaminated pond water through the dike structure will occur unless a mechanism is
provided to either restrict the actual water migration or attenuate the water borne contaminants. The
flow through a dike can be restricted either by controlling the hydraulic gradient that exists across
the dike (e.g., keep the water elevation equal on both sides), or by reducing the permeability of the
dike. Dye tracer studies performed in Great Lakes CDFs (Pranger, 1986) showed that discrete
points of significantly higher dike seepage were measured at several CDFs including Kenosha and
Manitowoc. At these facilities, the dikes were made of sheet pile cutoff walls within a rip-rap dike.
The discrete points of high discharge were thought to be due to localized failures of the cutoff wall.
At Milwaukee and Kewaunee facilities, zones of higher outflow were observed, but no discrete
points of high discharge were found. These latter dikes had cores of crushed limestone gravels and
sands. During this study it was also observed that significant decreases in outflow occurred in areas
where deltas of previously dredged material were placed against the dike within the CDF.
Design considerations to limit the release of contaminants through dike seepage are shown on
Figure 5.9. The design of dike seepage control systems must reflect the nature of the subgrade
upon which the dike is built. Vertical barrier systems must intercept and key into an underlying low
permeability soil layer (e.g. aquitard) that prevents contaminated ground water from flowing beneath
the barrier. Obviously the economy of a vertical barrier system is significantly influenced by the
depth of penetration required to intercept such a confining layer. Lacking a natural aquitard, a low-
permeability liner may need to be incorporated in the basin design.
Mechanisms to totally restrict water migration through the dike involve constructing either an
impermeable barrier in or on the dike consisting of either a low permeability soil, a geomembrane, or
a geosynthetic clay liner (see Appendix C for a discussion on geosynthetic barriers). Such
"hydraulic isolation", see Table 1.2, are used when either the concentrations of the contaminants are
high or when the potential of the contaminants partitioning to the water is high. The low permeability
soil barrier can be constructed using either a compacted clay liner (CCL) or geosynthetic clay liner
(GCL) designed into the CDF dikes or by an intentional operations placement of clean, fine grained
sediments against the surface of the dikes. While geomembrane and clay barriers will be highly
restrictive, the operationally placed barrier may be only partially restrictive depending upon the
sediment particle size and placement method.
Attenuation of water borne contaminants in the seepage may require both the removal of suspended
solids and dissolved contaminants from the effluent. The suspended solids can be allowed to settle
out of the effluent or can be physically filtered as described above. Removal of soluble
contaminants from the effluent may require changing the effluent water chemistry or filtering the
84
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In-Lake CDF
Seepage into Body
of water with mixing
and resulting dilution
Dike Seepage
of Effluent
Fluid Migration of
Suspended Solids
Coarse Granular
Material with
Little or no Fines
Pumping to Limit
Flow Gradient
Upland CDF
Seepage of leachate
into foundation soils
with minimal dilution
Transport of
Dissolved Contaminants
No Attenuation
Granular Non-Reactive
Material with Little
or no Fines
r
Figure 5.9
Seepage of Effluent Through Dike
Appendix A.2 Soil Chemistry
"1
Precipitation of
Contaminants
(Heavy Metals)
Pore Water tends to
become basic due to
use of Crushed limestone
as dike material.
Cations and Ions
Attach to Clay
Particles
L.
Adsorbtion and Absorbtion
of Organic Contaminants
of Fine Grained Particles
.J
85
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water through a treatment system..
5.1.3 Foundation Seepage of Leachates
The migration of partitioned contaminants into the foundation soils involves two different
mechanisms as shown in Fig. 5-10. These two mechanisms are: (1) advective transport of
suspended particles or dissolved contaminants, and (2) diffusion. Laboratory and field
investigations sponsored by the USAGE (Chen et al, 1978) clearly showed that leachate problems
can exist even when effluent quality is acceptable. For the particular CDFs monitored, the leachate
showed high levels of ammonia, nitrogen, iron, and manganese in facilities where the supernatant
and effluent had very low concentrations. This work concluded that the physical and chemical
properties of soil underlying the CDF should be considered. Leachate entering the foundation soils
will undergo less dilution than seepage passing through the dike structure for in-lake or shoreline
CDFs. Such potentials for contaminant migration may require use of the "hydraulic isolation" option
previously discussed on Table 1.2.
Advective transport of contaminants into the foundation soils is caused by the flow of leachate under
Darcy's Law. The rate of flow is controlled by hydraulic gradient (change in hydraulic head divided
by flow length), and the permeability of the soils. Shoreline sites are commonly associated with
groundwater discharge zones (e.g. wetlands) that have natural upward flow gradients. Such natural
upward flow gradients minimize leachate migration into foundation soils beneath a CDF located at
such sites. Leachate migration into foundation soils is driven by these natural hydraulic gradients
and the heads produced by the varying depth of effluent within the CDFor infiltration and excess
pore pressures generated during placement of dredged sediments. The extent or significance of
surface infiltration is dependent upon whether 2 final cover is in place or interim conditions exist.
During interim periods where the dredged material is exposed, the advective mobility of
contaminants may be greater due to the chemical actions of acid rains or oxidation related
breakdown of contaminants.
The actual flow of contaminants into the foundation soils is controlled by the three different types of
barrier conditions which can exist at the limit of the dredged material. These are: (1) restricted - no
flow barrier, (2) partially restrictive barrier, and (3) unrestrictive barrier. The fully restricted or no flow
barrier is typically the result of a CDF foundation liner of compacted clays or a geomembrane. In
contrast, a partially restricted barrier can be a function of site stratigraphy, site hydrogeology, or the
presence of a filter media at the bottom of the CDF. The filter media can be constructed of a clean
sediment layer on filter fabric (refer to Appendix C for a discussion of design procedure). An
unrestricted barrier is typically comprised of clean granular foundation soils.
The advective transport of soluble contaminants in the leachate can potentially undergo attenuation
depending on two different processes. These processes are: (1) attachment of anions/cations to
clay minerals, and (2) adsorption/absorption of organic contaminants on humic materials. A detailed
discussion of the attenuation of contaminants in soils and soil-like materials is presented in Section
86
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Foundation Seepage
of Leachates
Fluid Migration of
Suspended Solids
Driving mechanisms involve
hydraulic head produced
by height of pond water
in CDF and pore pressures
generated by compressing
dredged material. Head
may be minimized by
natural inward gradients
where CDF is located
within zone of groundwater
discharge.
1- Geomembrane
2- Clay Barrier
1 Clean Sediment layer
? filter Fabiic
3 Site Stratigraphy Dependen
Granular Material w/o Fines
Transport of
Dissolved Contaminants
* No Attenuation
r
Appendix A.2
Cation and Anions Attach
to Clay Particles
Adsorption and Absorbtion
of Organic Contaminants
on Humic Materials
L.
.J
Figure 5.10 Control of Foundation Leachate Generation
87
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2 (Soil Chemistry) of Appendix A.
Diffusion transport of dissolved contaminants is driven by concentration gradients and is evaluated
using Picks First Law. This contaminant transport can occur in the absence of water movement.
Fortunately, the concentration of contaminants within most leachates is very low and does not lead
to significant diffusion rates.
5.1.4 Run-Off Contaminant
As shown on Figure 5.11, precipitation falling on a CDF can contribute to contaminant migration by
increasing infiltration and surface water run-off. The acidic nature of precipitation in Region 5 may
lower the pH of the exposed dredged material and supernatant and place more metal contaminants
into solution. The potential for contaminant transport due to run-off is influenced by whether the
dredged material remains exposed to air during interim operations such that geochemical changes
in the sediments are possible, and whether a final cover has been placed over the dredged material.
During interim operations, the surface water run-off over air exposed dredged materials can cause
significant erosion losses if no vegetation or significant slopes exist. Contaminant losses from run-
off during the interim operations period can be reduced by providing surface vegetation, limiting
slopes to less than 5 percent, and ensuring that run-off does not over top perimeter dikes. It
should be noted that interim operations may last several decades so that the vegetation of exposed
dredged materials may be very cost effective. During this same period, settlement of the dredged
material may result in ponds forming within the CDF. Such ponds provide the potential for plant and
animal uptake as discussed in Section 5.2.
Once a clean final cover is placed over the dredged material, the significance of surface water run-
off as a contaminant transport mechanism is eliminated. The presence of a thick vegetative layer
improves the resistance to soil erosion and the removal of suspended solids and soluble nutrients
such as ammonia, nitrogen, and soluble phosphorous (Chef, 1978). Such run-off will have had no
contact with contaminants if a barrier layer is incorporated in the final cover and therefore would not
be a potential contaminant transport mechanism.
The primary control of the surface water run-off contaminant pathway is conventional erosion control
practices such as limiting slopes and surface vegetation. A typical erosion control program will
include limiting slopes to <5%, vegetation of cover surfaces with native grasses and temporary
containment of all run-off in sedimentation basins.
5.2 Contaminant Pathways to Plant and Animal Communities
Contaminant pathway considerations for plant and animal communities are presented in this section
using the general food web flow relationships presented on Figure 5.12. Such food web flow
diagrams show the general movement of nutrients and contaminants within and between the plant
88
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Pathways
LEGEND
Uncompleted
CDF
Infiltration
A Evaporation
Surface Water
Runoff
Infiltration"]
1
Evaporation
Surface Water
Runoff
Erosion of Cap
Overtops Dikes
Erosion of Cap
Contained by Dikes
Ponding on Surface
Change pH and
put Heavy Metal
in Solution
Becomes Part of
Effluent in Pond
Erosion of
Dredge Material
Development of
Plant Species
Change pH and
put Heavy Metal
in Solution
Volatilization of
Organics
Development of
Plant Species with
Potential for
Uptake Containment
Direct Discharge
of Runoff
Runoff in Effluent
Discharged at Weir
Figure 5.11 Surface Water Mechanisms Related to Precipitation on CDF
89
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V'ATMOSPHERE
MIGRATION
ORGANISMS
IN WATER
COLUMN
DETRITUS '
WATER
COLUMN
BENTH1C
ORGANISMS
TH1CC -
ATER -
SEDIMENT i.;
WATER
SEDIMENT
j^^GROUNDWATER j ^%
'""^v ^tt^li^^11^^^^'-"^'1-'-^ :' '- "'
(Adapted From Seliskarand Gallagher, 1983)
Figure 5.12 Food Web Drawing Showing General Flow of Nutrients and Metals
90
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and animal community. This movement can be "up" the food chain, e.g. fish in ponds within the
CDF, or "down" the food chain, e.g. excretion or death. Such movement of contaminants by
biological mechanisms is in addition to the movements caused by the non-biological flow shown on
Figure 5.1. These non-biological movements are discussed in Section 5.1.
The uptake of contaminants by plants and animals can be estimated by the use of simple
mathematical relationships presented in Table 5.1, (Kelly, 1988). As shown on Table 5.1, the larger
the animal bioconcentration factor (BCF) or Plant Uptake Factor, the greater the amount of
contaminant absorbed. The various bioconcentration factors (BCF) and Uptake Factors associated
with specific chemicals are discussed in sections 5.2.1 and 5.2.2.
Contaminant pathways to plant and animal communities must be considered during both the
operational and post-closure time periods. In particular, ponds that form on the dredged materials
during the decades long operation of the CDF may offer the most significant opportunities for plant
and animal uptake. The ability to limit these contaminant transport mechanisms prior to placement
of the final cover should be evaluated.
The control of long-term contaminant uptake by plants requires a final cover over the problematic
dredged materials that controls the movement of the plant roots into the dredged material or limits
the capillary rise of leachate in the final cover. The movement of roots into the waste can be
prevented by the use of a geomembrane barrier or a clean soil cover that has a total thickness
greater than the maximum root depth of the target vegetation. The capillary rise of contaminated
water from the dredged materials can be limited by the use of a geomembrane or capillary break in
the final cover. The capillary break can be formed using a coarse granular sand or gravel layer and
could be formed with dredged material. Section 5.2.1 presents a general background on factors
influencing plant uptake of contamination.
Limiting the long-term uptake of contamination by animals is accomplished if plant uptake is
prevented and burrowing of animals into the cover is discouraged. Burrowing by animals can be
prevented by the use of a geomembrane or biotic barrier in the final cover. Typical a biotic barrier
consists of a layer of stone, with each stone weighing more that the target animal can lift or move.
Section 5.2.2 presents general background of factors that influence animal uptake of contamination.
5.2.1 Contaminant Uptake by Plants
Contaminant pathways for plant uptake are illustrated on Figure 5.13 for terrestrial, submergent, and
emergent plants such as eelgrass, duckweed and bulrush. Vegetation production is primarily a
function of light, soil moisture, nutrients, and interactions with surface water and soil microbes.
There are 16 elements that must be absorbed by all plant life in order to complete a full life cycle
(National Nutrients, 1988). These include the major elements oxygen, hydrogen, carbon, nitrogen,
phosphorous, and potassium; secondary elements are magnesium, and sulfur; and the
micronutrients include iron, boron, copper, manganese, chlorine, zinc, and molybdenum. The
91
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TABLE 5.1
Summary of Contaminant Uptake Relationships For Plants and Animals
A. Dredged Material - Plant
CP = Uptake Factor x Cs
B. Plant - Animal (grazer)
Cag = Cp x BCF
C. Dredged Material - Soil Biota (Direct Ingestion)
Csb = CsxBCF
D. Animal (grazer or predator) - Animal (Predator)
Cap = Cag x BCF or Capafler = Capbefore x BCF
Nomenclature
Cag - animal (grazer) tissue concentration (ug/g)
Cap - animal (predator) tissue concentration (ug/g)
Cs - chemical concentration in dredged material (ug/g)
Cp - chemical concentration in plant tissue (ug/g)
Csb - chemical concentration in soil biota (ug/g)
*BCF - bioconcentration factor (unitless)
*Uptake Factor - chemical uptake rate by plant (unitless)
Notes: * - chemical specific value obtained from literature
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CDF without Cap
Depending
on
Species
Minimal Uptake
of Contaminants
Roots Penetrate
Into Dredged Material
Plants without
Tap Roots
Root Structure Not
in Dredged Material
No Uptake of Contamination
from Dredged Material
Depending
on
Species
Minimal Uptake
of Contaminants
Roots Penetrate
Into Dredged Material
Plants without
Tap Roots
Roots Penetrate
Into Di edged Material
Figure 5.13
Mechanisms Involved in Plant Uptake of Contaminants in Capped and Un-Capped CDF's
93
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micronutrients are typically required by plants in concentration of less than two parts per million
(ppm) (National Nutrients, 1988). The mechanisms involved in the uptake of contaminants by plants
are dependent both on whether the plants roots extend into dredged material and on the particular
plant species. The bioavailability of an element or contaminant can be increased by the following
(Maybecket. al. (eds.), 1989):
1. Small particle size
2. Aqueous/lipid solubility
3. Complexation
4. Specific active processes for elements or complexes which mimic essential
nutrients.
Interactions between various metals and other contaminants can vary for a given plant (or other
organisms) and media, and can be controlled by pH and other factors. Organic contaminants
typically have large molecules that cannot pass through the cell walls of plants, thus limiting uptake.
Bursztynsky (1981) notes 6 primary biochemical pollutant uptake and removal processes in wetland
vegetative systems. These are:
1. Uptake through plant - soil interface via roots, rhizomes, holdfasts and buried
shoots and leaves.
2. Uptake through plant - water interface via submerged roots, stems, shoots, and
leaves.
3. Translocation through plant vascular svstem, from roots to stems, shoots, leaves,
and seeds during the growing season.
4. Differential pollutant uptake, such as preferential storage of trace contaminants in
specific plant parts and preferential uptake/accumulation of certain trace elements.
5. Nonspecific pollutant uptake, occurring primarily as plants absorb large quantities of
nutrients from water and sediments.
As the main sources of trace elements to plants are their soils or nutrient solutions, Kabata-Pendias
and Pendias (1984) conclude that plants readily take up metals dissolved in soil solutions in either
ionic or chelated and complexed forms, and binding of metals to soil constituents is one of the most
important determinants of availability. For example, these authors note that metals adsorbed onto
clay minerals are most readily available to plants, compared to those fixed by oxides or bound onto
microorganisms, in general. Plant absorption can be summarized as (Kabata-Pendias and Pendias,
1984):
1. Capable of operating at very low concentrations in solution.
94
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2. Depends largely on the concentration in solution (esp. at low ranges).
3. Depends strongly on the occurrence of hydrogen and other ions.
4. Varies with plant species and stage of development.
5. Selective for a particular ion.
6. Accumulations of some ions take place against a concentration gradient.
7. Micorrhizae play an important role in cycling between external media and roots.
A summary of typical plant uptake factors for chemicals in soils and sludge is presented in Table
5.2. A review of Table 5.2 indicates that the metals that have the greatest potential to be absorbed
by plant tissue are: arsenic, cadmium, nickel and zinc.
5.2.2 Contaminant Uptake by Animals
Contaminant animal uptake pathways are flow charted on Figure 5.13. There is an abundance of
data on the bio-effects on metals and to a lesser extent for other contaminants. EPA published the
Fourth Annotated Bibliography on Biological Effects of Metals in Aquatic Environments (Eisler,
1979) which lists 886 titles and abstracted material from research published in only a two year
period (1978 to 1979). Articles were selected for information on growth, bioaccumulation, retention,
translocation, histopathology, and interaction effects of metals and their salts in combination with
other substances. The first three volumes of this series covered previously published research.
More recently, the U.S. Fish and Wildlife Service has produced a series of Biological Reports on
metal and organic compound hazards to fish, wildlife, and invertebrates. These are synoptic
reviews of bio-effects and cycling data for specific metals. Of primary interest are Lead Hazards to
Fish. Wildlife and Invertebrates (Eisler, 1988), Cadmium Hazards to Fish. Wildlife, and Invertebrates
(Eibler, 1985), Chromium Hazards to Fish. Wildlife, and Invertebrates (Eisler, 1986), Mercury
Hazards to Fish. Wildlife, and Invertebrates (Eisler, 1987), Arsenic Hazards to Fish. Wildlife, and
Invertebrates (Eisler, 1988).
EPA sponsored a literature review titled Metal Bioaccumulation in Fishes and Aquatic Invertebrates
(Phillips and Russo, 1978) with separate chapters on 21 metals. This is a valuable collection of
bioaccumulation data up to 1978. In the section on conclusions and recommendations, it is noted
that some chemical forms of metals, such as methylmercury, are far more toxic and more readily
accumulated by aquatic organisms than are others, and that most bioaccumulative and toxic forms
of other hazardous metals should also be determined. This stresses the need to understand the
95
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TABLE 5.2
Typical Plant Uptake Factors for Chemicals in Soils and Sludge
Chemical
Arsenic
Cadmium
Chromium III
Copper
Lead
Mercury
Nickel
Zinc
Uptake Factor*
0.02
0.01
No significant uptake
No significant uptake
0.006
0.001
0.09
0.03
Plant Type
Chard
Carrot
Lettuce
Dry Legume
Lettuce
Leafy Vegetable
Soil Type
Sludge
Compost
Sludge
Sludge
Sludge
Comments
Based on dry weight of
plant and soil
Hg is highly bound by
humic substances.
Sludges can decrease
Hg crop concentration,
the exception is
mushrooms which
bioaccumulate Hg
(Domschet. al., 1976)
Reference
Chisholm, 1972
Maclean, 1978
Connor, 1984
Gary, etal., 1989
EPA, 1988
CAST, 1976
EPA, 1988
Chaney, etal., 1980
EPA, 1988
*Reference Equation B, Table 5.1
96
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chemical and physical movement of metals in the ecosystem along with the biological food web
movements.
Leland and Kuvabara (1985) state: "The classic idea of food chain enrichment developed from studies of
DDT and methylmercury (which have high affinities for lipids) where the highest trophic levels contain the
highest toxicant concentrations, does not hold for most heavy metals." More typical distributions show that
sediment-feeding organisms contain higher metal concentrations than do other consumers because
sediments generally contain higher concentrations of heavy metals than are present in aquatic organisms
(Leland and Kuvabara, 1985). This thinking is illustrated with a study by Armstrong and Hamilton (1973)
which showed that concentrations of mercury in preferentially occur detritus feeders, omnivores, or taxa that
feed primarily on benthic invertebrates (Leland and Kuvabara, 1985). A summary of typical
bioconcentration factors for fish and animals is presented in Table 5.3.
5.3 Airborne Emissions Control
The control of airborne contaminant emissions includes limiting the direct volatilization of contaminants into
the air and the wind related loss of soil particles that are contaminated. The direct volatilization of
contaminants in to the air is a potential problem when the dredged materials are exposed to the
atmosphere. Thus the volatilization of contaminants during the operation of the CDF can be limited by
maintaining the material level within the CDF below the water elevation. For upland CDFs and where
hydraulic or evaporation considerations prevent such action, the exposed contaminated dredged material
can be covered with clean dredged material to limit volatilization.
In a similar manner, the wind erosion of the dredged material is controlled by limiting the exposure of the
contaminated dredged material. If historical si"-face wind velocities and the grain-size distribution of the
dredged materials indicates significant wind erosion (e.g. a large percentage of solid particles having and
effective diameter less than 10 microns), then the use of a clean granular soil cover over air exposed
dredged materials is recommended. The generation of significant wind erosion (See Section 2.3.6) must be
avoided during the operations and post-closure periods.
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TABLE 5.3
Typical Chemical Bioconcentration Factors in Animals
Chemical
Arsenic
Cadmium
Chromium III
Copper
Mercury
Inorganic
Organic
Nickel
Zinc
Bioconcentration
Factor (BCF)*
No significant uptake
0.00002
0.4
No significant uptake
0.0001
0.85
5.0
No significant uptake
0.01
Comments
Cattle, muscle tissue, sludge study, chicken eggs
Guinea pigs, fed Swiss chard grown on sewage sludge.
Tissue: muscle
Vole, Tissue: muscle
Cattle, muscle
Mice
Mink, Tissue: muscle
Mammals have a mechanism to limit intestinal absorption
Guinea pigs, fed Swiss chard grown on sewage sludge.
Tissue: muscle
Reference
EPA, 1988
EPA, 1988
Furretal., 1976
Williams et al , 1978
Johnson et al., 1981
Fitzhughetal., 1980
Auerlich et al., 1974
Goughetal., 1979
Furretal., 1976
*Reference Table 5.1
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SECTION 6
CDF BASIN DESIGN RECOMMENDATIONS
Conventional CDF design focuses on retention of sediment solids within the facility. Depending
upon the nature of the site, the contaminants of concern, method of dredging, physical
properties of the dredged material, operational aspects, and many other factors including socio-
political, supplemental environmental design criteria may be required for the CDF. This section
presents design alternatives to control contaminant loss from the CDF basin through (1)
effluent or leachate discharge through the dikes, and (2) leachate drained from the sediments
that discharges into the groundwater. The designs must satisfy the AEPP given in Section
2.2.1 for effluent quality and Section 2.2.5 for groundwater leachate quality. These design
alternatives include both the use of additional designed components and the use of operational
constraints. These two pathways are the most significantly impacted by partitioning of the
contaminants to the supernatant waters. The use of "hydraulic isolation" design criteria is
such cases has been previously discussed (see Table 1.2 and related discussion). The
remaining pathways are impacted by interim and final closure and are discussed in Section 7.
Additional design considerations may pertain to the CDF basins in new "hybrid" CDFs that have
been proposed as a closure system for coastal Superfund sites, e.g., Indiana Harbor. The
presence of existing contamination beneath the CDF basin may result in pathway design
considerations not fully developed herein.
The containment basin of a CDF is formed by the perimeter dikes and the subgrade of the site.
Water can potentially leave the basin as a non-point source by either seepage through the
perimeter dikes or by leaching into the underlying subgrade. The control of either pathway is
therefore dependent upon limiting hydraulic gradients and/or the design of a barrier to limit
advective transport of contaminants, or design of a filter to attenuate the flow of the dredged
material itself. Hydraulic gradients may be significantly influenced by the type of CDF, e.g. in-
lake CDFs typically have very low gradients as compared to high gradients common to upland
CDFs.
6.1 Effluent Discharge Through the Dikes
Water carried by the dredged sediments must be removed from the CDF to provide space for
additional sediments and to develop a stable base for construction of the final cover over the
dredged material. Effluent can leave the CDF by seeping through perimeter filter dikes or
through a weir point discharge system. The latter is particularly attractive if the effluent must
be processed to remove or attenuate contaminants. The design of point-source effluent filter
and treatment systems has been discussed in Sectjon 5.1.1 and will not be elaborated on in
this section. Monitoring of effluent release through conventional CDF dikes (Schroeder, 1984)
indicates that point discharges from porous zones in the dikes occur rather than uniform
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TABLE 6.1 DIKE BARRIER SYSTEM APPLICATION IN CDF'S
O
o
CO
L-
CD
'l__
v_
D
00
"^
.*-*
'25
0
CD
E
1
CD
CL
"^
O
Barrier System
Compacted Clay Liner (CCL)
Geomembrane Liner (GML)
Geosynthetic Clay Liner (GCL)
Geomembrane Cut-off Wall
Bentonite Slurry Cut-off Wall
Fabric Form w/ Grout
Clean 'Fine' Sediments
Clogged Geotextile
Graded Soil Filter
Fabric Form w/Sand
Barrier
Location*
C
C
C
A
A
C
C
C
B
C
COE
Usage
X
X
X
X
In-Lake
CDF
N/A
O
N/A
O
o
Shoreline
CDF
N/A
O
o
Upland
CDF
N/A
N/A
N/A NOT APPLICABLE £ Good Application Q Maybe Difficult to Construct
* Barrier Locations
Dredged
Material
-------
Effluent
Discharge
Restrict Effluent
Discharge Through
Dike Structures
Designs Using Initially
Impermeable Materials
Designs Employing
A Clogging Mechanism
Liner
Technology
Wall
Technology
Natural
Geosynthetic
Compacted
Clay (CCL)
Geomembrane
(GML)
Fabric Form Geosynthetic
w/Grout Clay (GCL)
Geomembrane
Cut-off Wall
Bentonite
Slurry
Cut-off
Wall
Graded
Soil
Filter
dean
Fine
Sediments
Geotextiles
Fabric
Forms
w/Sand
Monitoring
Requirement
Monitor outside perimeter of dfee structure for
discrete effluent discharge using acoustical echo tracking.
Figure 6.1 Effluent Dike Discharge Control
-------
seepage along the entire dike structure. Such findings may require the use of an alternative
mixing zone definition if the point discharges cannot be characterized or eliminated.
Effluent seepage through the dikes can be limited by controlling the level of effluent within the
CDF or by designing an impermeable barrier layer into the dike as shown on Table 6.1 and
Figure 6.1. The flow of water beneath the dike can be controlled using an impermeable basin
liner or a dike vertical barrier that penetrates into a lower natural barrier layer. Note that,
within Region 5, the COE has already used geomembranes, filter fabrics (geotextiles), and
bentonite slurry cut-off walls in perimeter dikes, see Section 4. A more detailed discussion of
geosynthetic components is presented in Appendix C. No one barrier system is suitable for all
CDF applications as discussed below.
6.1.1 Dike Barrier Systems
Compacted Clay Liner (CCL) - A CCL barrier is a principle EPA containment element used in
the design/construction of solid and hazardous wastes disposal facilities. It is well suited to
most upland CDF applications. Construction of the CCL presents significant, if not
insurmountable, problems in an aqueous environment. No current method of construction
allows placement of a CCL beneath water. Use of a CCL in shoreline and in-lake CDFs would
require a perimeter cut-off system and pump out that would allow placement of the CCL on a
dry, prepared subgrade. Such construction requirements could be prohibitively expensive for
structures such as CDFs because of their significant perimeter lengths.
Construction costs of CCLs are very dependent upon the availability of fine grained soils
suitable for use as a barrier. If suitable soils are available on-site, the placement of the CC!
will typically cost $8 - $16 per ton. Frequently the on-site soils are amended with bentonite to
reduce their permeability. Amendment costs are approximately $10 - $15 per ton in addition
to placement costs (Richardson, 1995).
Geomembrane Liner (GML) - A GML is the least expensive of the barrier alternatives and is
also a principle EPA containment element for RCRA applications. The GML (see Appendix C)
can be constructed with a flexible geomembrane such as PVC that allows factory fabrication of
large panels or from high-crystalline thermoplastics such as HOPE that must be welded
together in the field. GMLs such as HOPE offer greater service life and resistance to chemical
attack of the polymer. While the resistance of a GML to chemical attack can be evaluated
using the EPA 9090 test, the low contaminant concentration levels associated with
problematic sediment should not impact most commercial GMLs. As with CCLs, the placement
of GMLs has commonly been done only in dry site conditions. Several significant problems are
possible if installation of a GML is attempted below water:
1. The polymers have specific gravities less than 1.0 and will float, necessitating
the use of counterweights;
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2. The presence of moisture on the geomembrane reduces the quality of a field
seam; and
3. Soil or stone placed over the GML can easily puncture the geomembrane and
inspection or repair of the geomembrane is not feasible under water.
In addition to aqueous application problems, the design of a GML must address problems
associated even with 'dry' applications. The most significant conventional problem generated
by the GML is sliding stability due to the slick surface of the GML. The COE experienced a
sliding failure during their placement of a GML during the construction of the Chicago CDF.
Interface friction tests under saturated conditions must be performed as part of the design
process.
Installed costs of GMLs range from $0.40 to $0.80 per square foot depending upon the type of
geomembrane and difficulty of installation (Richardson, 1995).
Geosynthetic Clay Liner (GCL) - GCLs use a thin layer of bentonite attached to a geotextile to
form a barrier layer. GCLs must be placed in dry site conditions to prevent premature hydration
of the bentonite granules. This wetting-up of the GCL dramatically increases the weight and
reduces the strength of the GCL. In upland CDFs, the GCL is an economical substitute for the
CCL averaging approximately $0.85 per square foot to install. The GCL is simply rolled out like
carpeting to line dry installations. Commonly a 6-inch overlap is used between adjacent panels
of GCL such that field welding or seaming of the panels is not required. The installed GCL
would require protection from current or impact forces resulting from placement of the dredged
material in the CDF.
Marine application of GCLs has never been attempted and would require a GCL manufactured
for such an application. A marine GCL would require a significantly stronger carrier geotextile
to survive the higher installation forces that could be anticipated due to hydration of the
bentonite during placement. Once submerged, the buoyant weight of the GCL would reduce
the force in the geotextile. Alternatively, the bentonite would require treatment to retard the
rate of hydration to limit swelling and subsequent loss of strength of the clay. If allowed to
hydrate, the bentonite must be securely fastened between two layers of geotextile carrier.
This may require stitching of the fabrics together. Such options are available from GCL
manufacturers.
Geomembrane Cut-off Wall (GCW) - A GCW is constructed using HOPE panels that are
attached by interlocking fittings at their edges. The interlocks are similar to that found on
conventional sheet-piling but include a hydrophilic seal that swells when exposed to water.
The GCW is installed in sandy soils using a vibrated steel guide. In clays or loams, the GCW
are typically installed using a bentonite-slurry trench to penetrate the confining clay layer and
103
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seal the toe of the cutoff wall. The GCW provides increased chemical resistance and longevity
when compared to conventional steel sheet-pile barrier walls.
The cost of GCW installation is dependent on the soil type that it must penetrate and the depth
of penetration required. In favorable soils, GCWs have been installed to depths exceeding 20
meters at costs less than $2.00/square foot. Field construction quality assurance procedures
have been established to verify the integrity of the interlocked joints (EPA/540/R-92/073).
Bentonite Slurry Cut-Off Wall - The bentonite cut-off wall system has been extensively used
to laterally contain Superfund remediation sites. A water-bentonite slurry is used to maintain a
trench excavated with a backhoe or clamshell. The permanent barrier is made using either a
soil-bentonite blend or a soil-cement-bentonite blend. This soil-bentonite blend is placed into
the trench and displaces the lighter bentonite-water slurry. Construction of the slurry wall
must be performed under dry conditions but can easily extend below the groundwater
elevation. Thus, aquatic CDFs could use this cut-off method if their dikes were, at least
initially, built with a portion above the water elevation and impermeable enough to contain the
slurry.
Bentonite cut-off walls require no special construction equipment for depths less than 30 feet.
Greater depths can be accomplished, but will typically require the services of an experienced
specialty contractor. Slurry wall construction costs are heavily dependent upon the depth of
the wall. Costs in 1991 dollars, range from $7.00 per square foot for a 30-foot deep walls to
$15.00 per square foot for a 75+ foot deep wall (EPA, 1992).
Fabric Form with Grout - While more commonly associated with erosion control, the use of
geotextile forms and a bentonite enriched grout can produce a hydraulic barrier blanket. The
fabric form uses two woven fabrics that are connected by threads at regular increments such
that a blanket of controlled thickness is produced when grout is pumped between the fabrics.
The fabric forms can be placed beneath water if weighted to reduce their buoyancy.
Installed cost of grout-filled fabric forms in conventional applications is approximately $2.00
per square foot. The addition of bentonite to the grout and the need for counterweights will
probably raise this cost significantly in aquatic applications (Richardson, 1995).
Clean 'Fine1 Sediments - A moderately low permeable barrier can be formed using silty
sediments that have been hydraulically dredged. As these sediments consolidate under their
own weight, their permeability will decrease. This operations-based liner offers significant
economy for sealing CDF bottoms (see Section 6.2) but may be difficult to use for dike lining.
The lining of a dike using this method would require using a dredge, earthmover or dragline
bucket to move the consolidated sediments from the CDF bottom to the dike sidewall and use
of a graded natural filter or geotextile to prevent the piping of the sediment through the dike.
This process may have to be repeated if erosional forces act on the side slopes prior to
104
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placement of dredged material against the dike. The use of clean fine-grained dredged materials
to line the CDF is an example of a containment alternative that can be implemented with a
simple change in operational practice.
Clogged Geotextile - Filter design criteria and laboratory tests are available (see Appendix C)
to select a geotextile that will not clog when used to filter a soil/water slurry. Conversely
these same methods allow a geotextile to be selected that will intentionally clog when exposed
to the sediment slurry. Such a barrier may require an initial clean slurry to develop clogging if
an initial small release of contaminants is unacceptable. As the geotextile clogs, a soil cake
can build up on the fabric and act as a flow barrier.
Geotextiles are the least expensive of the geosynthetic components and are commonly installed
for $0.10 to $0.1 5 per square foot. Counterweighted to resist floating and installed in a
aquatic application, the geotextile installed costs will be significantly higher (Richardson,
1995).
Graded Soil Filter - From the early works of Terzaghi, geotechnical engineers have known how
to design layered soil filter systems that allow movement of water with minimal loss of soil
particles. The COE relies on these very principles in the design of conventional CDFs. As in
the case of the geotextiles, these same relationships allow the design of a layered soil system
that will clog and prevent the flow of water.
The design for clogging requires only a slight modification of the COE design procedure for
dikes. As with the geotextiles, the use of an initial clean slurry may be necessary to clog the
system without allowing the escape of contaminants. While such a barrier would not provide
the very low permeability of CCLs or GMLs, they may provide an increase longevity without
any change in CDF construction costs.
Fabric Forms with Sand - Fabric forms could be filled with a fine sand (e.g. sugar sand) to
produce a soil layer that is readily clogged by fine sediments. A promising variation is the use
of a coating to seal the lower geotextile such that it acts like a geomembrane. The coated
fabric form could then be installed by counterweighting the fabric form panels, sinking and then
filling tne forms with sand. Adjacent form panels could be sewn together in a manner similar
to the construction methods used by the COE to place reinforcement geotextiles at sea for the
construction of embankments on soft foundations. This method has been used already to
reinforce CDF perimeter dikes. Such a system would provide a sand cushion to protect the
barrier membrane, and could be installed in all categories of CDFs.
Addition of a coating to the fabric form will add $0.30 to $0.80 per square foot to the cost of
the uncoated geotextile form. This increase in form cost may, however, be offset by a
decrease in the cost of the sand filling as compared to a bentonite grout filling.
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6.1.2 Design Considerations for Dike Barrier Systems
Integration of barrier systems into CDF dike sections must (1) not impair the stability of the
dike, (2) allow construction of the barrier using conventional construction technology, and (3)
key into a lower low permeable layer to minimize effluent discharge beneath the dike.
Stability of the Dike - The importance of barrier element stability within a dike has been
demonstrated at the Chicago CDF. The design dike section, shown on Figure 6.2a,
incorporates an impervious membrane beneath the armor stone on the disposal side of the dike.
Placed on the 3H:2V slope (33.8° slope angle), the membrane creates a sliding failure plane
due to its surface smoothness. Typical interface friction angles for various membranes range
from as low as 8 degress for smooth sheet to as much as 28 degrees for textured sheet. A
prior knowledge of the low interface friction values for such membranes would have alerted the
designer to the eventual sliding failure that developed.
The membrane stability problem at the Chicago CDF could have been eliminated by using a
barrier system that has a higher interface friction angle, by reducing the slope angle of the
membrane, or by increasing the thickness of the disposal side armor stone such that it would
have been self buttressing. Note that the prepared limestone had up to 6Vz inch stones that
would preclude placement of a vertical barrier system and presented a major threat to
membrane survivability during construction. Barrier systems offering higher interface friction
angles include a non-woven geotextile or graded soil filters. Such systems can be designed to
be clogged by the effluent. Alternatively, the layers of "B" and "C" stone on the disposal side
could have been replaced with a grout filled fabriform barrier that provides both erosion control
and a low permeability barrier, see Figure 6.2b. Alternatively, the slope stability can be
increased by reducing the slope angle of the geomembrane or increasing the thickness of the
interior stone. Howfwer, these design changes would significantly increase the cost of the
dike.
Following failure of the membrane, the COE opted for an 'operations' solution that should be
considered in future design alternatives. This operations solution simply called for the
placement of a stable wedge of clean sand against the interior of the dike prior to placement of
dredged materials within the CDF, Figure 6.2c. This alternative is both acceptable and
economical but does require providing a means of limiting the piping of the sand through the
large stone and renourishment of sand that has eroded prior to placement of additional dredged
materials. This sand layer may provide a sufficient filter layer to provide for "solid retention" of
problematic dredged materials. To increase the degree of "hydraulic isolation," a layer of clean
dredged material high in fines could be placed over the sand. As discussed in Section 6.2,
many dredged materials, once consolidated, produce very low permeabilities and make
excellent environmental liners.
106
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IWOUt
. -I1
A. Chicago CDF Dike Section
B. Grout Filled Fabric Form Barrier
C. Clean Sand Effluent Barrier
Figure 6.2 Alternative Dike Section Barriers
107
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Construction of the Dike - The dike barrier selected must be compatible with the proposed dike
zone materials. For the Chicago CDF dike section shown on Figure 6.1 a, the gradation
specifications for the prepared limestone core zone provide for up to 61/z inch stones and less
than 5 percent fines. This produces a high permeable core that would not lend itself to slurry
wall excavation or the use of vibratory hammer installation techniques. Thus the construction
of a vertical barrier through the prepared limestone would be very difficult and require unusual
construction techniques.
Integration of a barrier system within a conventional CDF dike is complicated by the zoned
construction that typifies such structure. The Buffalo CDF dike section shown on Figure 6.3a
is not unusual in its use of layered zones that range from sand and gravel to 1 3-ton stone.
Penetrating vertically through such layers is very difficult and suggests that the barrier layer
must be added between existing zone layers. For example, the filter blanket (geotextile) used
on the Buffalo Dike could be extended to the low-permeable subsoil as shown on Figure 6.3b.
This 'filter' layer could then be intentionally clogged by placing a layer of clean, hydraulically
dredged silts and clays within the CDF. After clogging the filter fabric, contaminated dredged
materials could be placed within the CDF.
Leachate Flow Beneath/Under the Dike - A low permeability barrier in the dike is effective in
presenting off-site seepage of leachate only if the natural subsoil under the dike is also of low
permeability soils or if the site is within a region of groundwater discharge. If this is not the
case, the flow through the permeable lower strata can be stopped by either lining the floor of
the CDF, see Section 6.2, or by placing a vertical cutoff wall through the strata. The flow of
seepage from beneath the CDF is of particular concern since the contaminant concentrations in
seepaoe waters will be at equilibrium concentrations. Depending upon the potential for
partitioning of the contaminants to water, such concentrations can be significantly higher than
those predicted by the elutriate tests, see previous discussion in Section 1.
Construction of a vertical cutoff wall through a surficial marine sand layer requires the use of
conventional sheet pile walls or placement of a dike section that can be penetrated by a driven
or vibrated steel guide or mandrel. Such a penetrable dike section would be constructed of
sands or sandy-gravels that lend themselves to slurry wall construction techniques or the use
of a vibratory mandrel for insertion of the barrier sections. The Buffalo CDF dike section
shown on Figure 6.3a may lend itself to both slurry wall and vibratory mandrel construction
depending upon the grain size distribution of the granular fill making up the core.
6.2 Leachate Discharge to the Groundwater
The possible flow of contaminated waters into the environment through the bottom of the CDF
is site dependent. Shoreline CDFs may be located in areas of groundwater discharge such that
groundwater flows into the CDF and limits outward leachate movement into the environment.
For CDFs located where unacceptably contaminated leachate from dredged materials can move
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HARBOR
(CDF)
,15'.I
H hj-4.6'* Cone. Plug
~ K) 5'-9-13 Ton SIOM
4 6'- i -3 Ton Slon*
LAKE
205'*
Subioll StobUitalton
Rock
A. COE Buffalo CDF Dike Section
HARBOR
(CDF)
LAKE
105-9-13 Ton SIOM
46'- ^-3 Ton Slon*
205
SubMll SlakUliolton
Rock
B. Clogged Filter Fabric Barrier
Figure 6.3 Alternative Dike Section Barrier
109
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into the underlying soils, a barrier is required to seal the bottom. The basic barrier systems
previously discussed in Section 6.1 can serve this function, with the exception of those
appropriate only for vertical cut-off wall type systems. These barrier systems include
compacted clay liners (CCL), geomembrane liners (GML), geosynthetic clay liners (GCL),
clogged geotextiles, and graded soil filters. Figure 6.5 provides a guide to the selection of a
barrier to limit the release of leachate.
o
o
or
a
I0
"AVERAGE" CURVE
10
"UPPER
BOUND"
CURVE
,-4
! ° Conventional Consolidation
"7 Single Load Consolidation
,A Slurry Consolidation
o Direct Permeability
a Gravity Drainage
I Vacuum Drainage
Field Infiltration
icr5 icr6 icr7 icr8
Coefficient of Permeability, k (cm/sec)
10
-9
( after Krizek and Salem, 1 974)
Figure 6.4 Summary of Permeability Data for Toledo Dredgings
Construction of a bottom liner system in shoreline or in-lake CDFs would appear to significantly
favor the use of a clean fine-grained slurry placed into the CDF initially to intentionally clog the
native underlying soils. Extensive geotechnical data for dredged materials exists that clearly
shows they are capable of achieving field permeabilities low enough to equal the other natural
material barriers. Data shown on Figure 6.4 shows that dredged materials from the Toledo
CDF can have long-term permeabilities less than 1 x 107 cm/sec. The actual permeability
achieved is influenced by the plasticity of the dredged material and the loading that it
experiences. This slurry could be hydraulically dredged silty sediments selected to seal the
CDF and not specifically selected to meet a given dredging need. Operationally such a sealing
layer would only require an initial dredging operation contract that is specific about the type of
dredging to be performed (hydraulic), the type of sediments to be moved (fine grained), and a
period of time for placement and limited consolidation of the sediments. Ongoing placement of
sediments within the CDF increases the vertical effective stress acting on the sealing layer.
This increase in vertical stress further consolidates the sealing sediments and reduces their
permeability.
110
-------
Leachate
Discharge
Restrict Contaminant
Leachate Discharge
Through Bottom of CDF
Groundwater does
not Flow into CDF
Provide Seal
Groundwater Flow I
Into CDF
Designs Using Initially
Impermeable Materials
Designs Employing
A Clogging Mechanism
No Escape of Leach>ote!
into Environment Possill
CCL
GML
Monitoring
Requirement
Fabric Form
w/Grout
GCL
Natural
Geosynthetic
Install Monitoring Wells Inside CDF
After Final Cover Emplaced
Figure 6.5 Leachate Discharge Control
-------
6.3 Impoundment Basin Design Guide
The type of low permeable dike or ground water barrier required can be selected using Figure
6.6 based on criteria previously presented on Table 1.2. Such barriers are required if the
concentrations or potential for partitioning of the contaminants to water are high. The
economics of construction will favor those barriers commonly placed in nonaqueous site
conditions. Such barrier layers include CCL, GCL, and GML systems. A dike barrier layer is
required in shoreline or inlake CDFs only if the WQS of the dike discharge exceeds applicable
WQS beyond the zone of dilution. The zone of dilution should be estimated assuming random
point discharge through the dike unless the designed dike section is specifically designed to
prevent this occurrence.
A low-permeability barrier may be required between the dredged material and groundwater if
both significant mobile contamination exists within the dredged material and significant
potential for contamination of the groundwater exists. For example, a CDF sited on low-
permeability glacial tills would not require a groundwater barrier even if the problematic
dredged sediments were close to regulatory limits of contamination. This is applicable to all
CDF types and ground water discharge/recharge zones.
112
-------
CDF Characteristic*
Dike Barrier Alternatives**
Groundwater Barrier Alternatives**
Minimum Cont. in DM
Minimum Potential Cont. of GW
UP-CCL.GCUGML
SL or IL - None Required
None Required
Minimum Cont in DM
Maximum Potential Cont. of GW
UP-CCL.GCUGML
SL or IL - None Required
UP-CCL.GCL.GML
SL or IL - Layer of Clean,
Rne Grained DM
Minimum Cont. in DM
Existing Cont. of GW
UP-CCL,GCL,GML
SL or IL - None Required
None Required
CO
Maximum Coni in DM
Minimum Potential Cont. of GW
Maximum Cont. in DM
Maximum Potential Cont. of GW
Maximum Cont. in DM
Existing Cont. of GW
* Cont = Contamination
DM = Dredged Material
GW = Ground Water
UP-CCL.GCL.GML
SL or IL -
WQS OK - None Required
WQS Exceeded - See Table 6.1
UP-CCL.GCL.GML
SL or IL -
WQS OK - None Required
WQS Exceeded - See Table 6.1
UP-CCL.GCL.GML
SL or IL -
WQH OK - None Required
WCS Exceeded - See Table 6.1
None Required
UP-CCL.GCL.GML
SL or IL - Layer of Clean,
Fine Grained DM
None Required
** UP = Upland CDF, SL = Shoreline CDF, IL = Make CDF
Figure 6.6 Impoundment Basin Design Guide
-------
SECTION 7
INTERIM AND FINAL CLOSURE OF CDFs
The role played by the interim and final covers of a CDF is heavily dependent upon the nature of the
contaminant(s) of concern, particularly its partitioning potential, and the type of CDF environment. For
example, acidic rains common to the midwest can leach metals from the sediments and mobilize them.
Specific design objectives for the cover must therefore consider the potential partitioning of the
contaminants present, the impact of precipitation generated infiltration and run-off, and the long-term
environment at the CDF. The need for a "hydraulic isolation" cover can be based on the criteria
previously discussed in Section 1, see Table 1.2, and on AEPP criteria presented in Section 2.
The cover system selected for a CDF can influence all of the contaminant pathways that have been
evaluated in this document, with the exception of the effluent discharge during filling operations. As
such, the design of a cover system for a CDF must focus on minimizing the impact of such pathways
when required. It is assumed in this document that final CDF covers will be constructed above adjacent
water surfaces, e.g. no submarine final covers are considered. However, permit reviewers should
consider the full operational life of the CDF and ensure that the need for interim covers/pathway control
is evaluated. This is particularly important in proposed hybrid sitings of CDFs that would couple the
CDF design with the remedial needs of the proposed disposal site. Figure 7.1 lists cover related
pathway control systems.
Cover systems must also be designed to ensure low maintenance, be easily monitored, and be
economical to construct. Final covers are placed once the CDF is full and the dredged material is
stable enough that future settlements will not damage the cover. Interim covers may be required when
the facility is either inactive for a prolonged period of time or when the dredged material is unstable and
future subsidence could impair the function of a final cover. This section reviews the existing cover
criteria used by USAGE and EPA for CDFs or waste containment systems and concludes with a review
of alternate cover systems that use geosynthetic components and/or sediment disposal strategies.
7.1 USACE Closure Objectives
The long term use for a CDF closure is commonly selected by the local sponsor. Local sponsors are
typically a City, County, or State governmental agency. The local sponsor is required to provide all
lands, easements, and rights of way to the USACE for the CDF. Under the Diked Disposal Program
(PL 91-611, Section 123) for constructing CDFs on the Great Lakes a local government sponsor is
required. The local sponsor may have planned or implemented productive and beneficial uses for
CDFs. These uses include the development of recreational areas, new or expanded marinas, wildlife
refuges, etc. The planned development must be compatible with the structural integrity of the facility
and the types of sediments contained. These lands cannot be transferred from the local sponsor
without the approval of the USACE. In recent years, the USACE has phased out the construction
114
-------
Pothwoys
Design
Requirement
Design
Solution
Monitoring
Requirement
Surface
Water
1) Meet water quality standards
2) Prevent erosion
NCDM
COM
Conventional
Erosion/Sediment
Control Practices
NCDM
Monitor Turbidity
CDM
Monitor turbidity
and water quality
of surrounding
open water
CDF
Cover
Plant
Uptake
(1) Prevent uptake of
contaminants by plant
species that serve as
food for various animal
groups
NCDM
No restrictions
CDM
(1) Select plant species
that limit uptake and
root penetration
(2) Restrict volunteer
vegetation by harvesting
(3) Restrict ponding
NCDM
None
CDM
Conduct assessment
of uptake by species
during harvesting
Animal
Uptake
(1) Prevent bioaccumulation
NCDM
No restrictions
CDM
1) Restrict predators
2) Restrict ponding
3) Restrict burrowing
animal unless geosynthetic
FML present in cover
NCDM
None
CDM
Conduct bioassay and
assessment of growth
and reproduction
Notes: (1) NCDM - non contaminated dredged material
(2) CDM - contaminated dredged material
Figure 7.1 Cover Related Contaminant Pathway Control
-------
of CDFs under the authority of PL 91 -611. Future maintenance dredging will, however, still require
confined disposal. Future CDFs will be constructed under the operation and maintenance (O and M)
authorities of individual navigational projects. The extent of local participation and cost-sharing for such
projects will vary on a project by project basis. A summary of filled CDFs with local sponsor, cap
design, and intended use is given on Table 7.1. A review of this table illustrates that closure procedures
are very site specific. Additionally, unlike a typical upland landfill, a CDF does not typically receive
either a temporary cover or removable cover during the actual sediment placement operation. Final
uses of the CDFs range from wildlife habitats to municipal landfill sites.
Current USAGE design guidance for CDFs (EM 1110-2-5027) is to maximize the volume of CDF
available for sediment disposal by promoting consolidation and drying of the contained dredge
materials. Interim soil covers are not typically used because they are difficult to install, interfere with
the drying process and reduce storage capacity.
7.2 EPA Closure Objectives
The USAGE has played a significant role in the development of the current EPA hydraulic isolation
based closure programs under RCRA. The USAGE involvement has ranged from assistance in the
development of design guidance documents ( e.g. EPA, 1979 ) to development and continued support
of the HELP (Hydrologic Evaluation of Landfill Performance) computer model. The HELP model
evaluates the effectiveness of hydraulic barriers and has played a major role in the EPA closure
program. This USAGE technical assistance in establishing EPA closure criteria should aid in
establishing applicable closure technologies for CDFs.
7.2.1 RCRA Subtitle C Hazardous Waste Landfills
A significant impetus in the development of the basic EPA cover system resulted from the need to meet
requirements for RCRA facilities and Superfund sites under RCRA 40 CFR 264.310. Such covers are
applicable for the worst-case sediments identified previously on Table 1.2. RCRA specifies that a final
cover be designed and constructed to:
1) promote long-term minimization of liquids migration through the closed cap;
2) function with minimal maintenance;
3) promote drainage and minimize erosion or abrasion of the cover;
4) accommodate settling and subsidence so that the cover's integrity is maintained; and
5) have a permeability less than or equal to the permeability of any bottom liner system or
natural subsoils present.
116
-------
Table 7.1 - Summary of Closed CDFs in the Great Lakes (adapted from EPA, 1990)
Facilities
Cleveland
Dike #12
Small Boat Harbor,
Buffalo
Toledo
(Grassy Island)
Michigan City
Bayport
(Green Bay)
Clinton River
Frankfort Harbor
Grassy Island
(Detroit River)
Years of
Operation
1974-1979
1968-1972
1967-1978
1978-1987
1965-1979
1978-1990
(98% filled)
1982-1990
1960-1984
Capacity
(cubic yards)
2,760,000
1,500,000
5,000,000
50,000
650,000
370,000
30,000
4,320,000
Local Sponsor
Cleveland-Cuyahoga
County Port Authority
Niagara Frontier
Transportation
Authority
Toledo-Lucas Port
Authority
City of Michigan City
City of Green Bay
State of Michigan
State of Michigan
none, U.S. Fish and
Wildlife Service owns
land
Cap Design
None
6 ft of soil
None
Clay cap with top soil
cover
City of Green Bay
plans to cap site
Clay
Site to be seeded
when completed
none
Ultimate Use
Waterfront
Development
Wildlife area/parking
Wildlife/recycle as top
soil
Park Land (now
undetermined)
Industrial
development/marine
terminal facility
Public access site and
MDNR field station
Cherry orchard
Wildlife area
-------
Table 7.1(Continued) - Summary of Closed CDFs In the Great Lakes (EPA, 1990)
Facilities
Harbor Island
(Grand Haven)
Harsen's Island
Kidney Island
(Green Bay)
Monroe (Edison)
Port Sanilac
Village
Verplank
Whirlpool
(St. Joseph
Harbor)
Windmill Island
Years of
Operation
1974-1985
1975-?
PV/O
1979-1986
-1984
1979-1983
1974-n/a
1978-1990
1978-1988
Capacity
(cubic yards)
310,000
100,000
1,200,003
n/a
143,300
134,000
25,000
160,000
Local Sponsor
State of Michigan
State of Michigan
City of Green Bay
n/a - private site
Village of Port Sanilac
Verplank Coal and
Dock Company
State of Michigan
State of Michigan
Cap Design
none
restored to former soil
level and revegetated
none
none
none
none
none
none
Ultimate Use
Public use
Upland nesting habitat
for waterfowl
**/»
1 1/ tf
Wildlife habitat
Detroit Edison
Municipal Landfill
Not available
n/a
Park facility
00
-------
USAGE assisted in preparing a technical guidance manual for EPA to assist in implementation of the
RCRA requirements (EPA, 1985).
Under RCRA guidance, final covers as a minimum include a vegetated top cover, a middle drainage
layer, and a composite barrier that consists of a geomembrane over a 2-ft clay layer. The vegetated
layer must minimize the impact of erosion on the cover. The middle drainage layer serves to reduce
the hydraulic head acting on the barrier system, and the composite barrier prevents infiltration of
surface waters to the waste. The minimal cover configuration is shown on Figure 7.1a.
Supplemental layers to the RCRA cover were proposed by USAGE to provide for the collection and
removal of gases generated by the waste, and for biotic barriers to prevent intrusion into the cover by
burrowing animals. The full RCRA cover with these supplemental layers is shown on Figure 7.1 b. EPA
has issued final Minimum Technical Guidance (MTG) on RCRA covers (EPA/530/SW-89/047) that
agree with the above USAGE interpretation.
7.2.2 RCRA Subtitle 0 Non-Hazardous Waste Landfill Covers
EPA closure criteria for RCRA-D nonhazardous waste landfills were established on October 9,1991.
The promulgated regulations require that final covers for non-hazardous waste landfills have a
permeability less than or equal to the liner or natural soils beneath the waste. A minimal cover under
RCRA-D for an existing unlined facility consists of the following:
a 6-inch layer of top soil with vegetation; and an
18 inches of 10'5 cm/sec soil infiltration layer.
Such a cover profile may be appropriate for problematic sediments having moderate partioning
potential, see Table 1.2. For covers over landfills incorporating a composite liner, EPA has recently
(Federal Register June 26,1992) interpreted the closure criteria to simply require a geomembrane if a
geomembrane is used in the liner system. Covers incorporating a composite barrier including a
geomembrane are suitable for sediments having extensive partitioning potential, see Table 1.2. Thus a
landfill that uses a liner barrier layer consisting of a geomembrane over a 2-ft clay layer having a
permeability less than 1 x 10'7 cm/sec would only need a cover having a barrier layer consisting of a
geomembrane over 18-inch of 10~5 cm/sec soil.
The Subtitle D landfill cover for previously developed unlined landfills represents EPAs perspective on
what minimum waste containment should include. The soil cover layer has a minimum thickness of 6-
inches but must also be adequate to support required vegetation. This normally requires the use of
substantially more than a 6-inch soil layer to achieve. The adequacy of the top soil layer must be
verified using a long-term water balance model such as the HELP model developed by USAGE for EPA
(Schroeder, 1987, 1988, 1990).
7.2.3 Additional Regulatory Closure Criteria
119
-------
vegetation/soil
top layer
drainage layer
low hydraulic conductivity
geomembrane/soil layer
waste
\\// \l/x
\\//
O
0
O
0
o
60 cm
-^- filter layer
30 cm
*- 0.5-mm (20-mll)
60 cm fleomembrane
A. RCRA-C MinimumTechnology Guidance Cover
cobbles/soil
top layer
biotic barrier
(cobbles)
drainage layer
low hydraulic conductivity
geomembrane/soil layer
gas vent layer
waste
0^0 0 V o " « ' °
o G> 'D. 0>
60cm
geosynthetic filter
30cm
geosynthetic filter
30cm
-^ 0.5-mm (20 mil)
geomembrane
60cm
30cm
geosynthetic filter
B. RCRA Minimum Technology Guidance Cover
With Supplemental Layers
Figure 7.2 EPA RCRA-C Final Cover Guidance
120
-------
The low infiltration RCRA covers described in the previous two sections are required for facilities
receiving waste that is typically recently generated. Covers for the closure of in-situ wastes have
shown considerably more flexibility. This same flexibility may be appropriate for CDF closures since
sediment contamination is typically both at very low concentrations and due to a historic event(s).
CERCLA closures comply with RCRA ARARs but vary significantly depending upon the potential
exposure of the waste to either the groundwater or humans. This exposure concept is illustrated in
Figure 7.3. Required CERCLA closures range from the full RCRA MTG cover for sites having a
significant exposure of groundwater and humans, to a no action alternative for sites having no
groundwater or human exposure potential (EPA/540/P-91/001). Such a risk-based cover selection
is consistent with pathway control based design discussed in this document.
Under TSCA (40 CFR 761.65), a written closure plan for a PCB storage facility must be submitted
and accepted by an EPA Regional Administrator. Closure criteria for chemical waste landfills used
for disposal of contaminated soils with PCB concentrations equal to or greater than 50 WP (40 CFR
761.75) does not provide specific closure criteria. Within Region 5, the RCRA-C minimum
technology closure guidance is commonly used as a basis for selecting the closure design
components for TSCA facilities.
7.3 Design of Closures for CDFs
Based on Table 7.1, existing closure of CDFs is commonly achieved by seeding grass or allowing
volunteer vegetation to germinate in the last lift of dredged materials placed in the CDF. Typically,
dredged materials are rich in phosphorous, nitrogen, and potash which promote rapid growth of
vegetation. Only a limited number of closed CDFs incorporate a clay barrier layer in the cover. Only
the Michigan City CDF cover has both a clay layer and a surface top soil layer. This section
presents basic design concepts for closure? that may be required when problematic dredged
sediments are present.
7.3.1 Barrier Layer Design
For covers over contaminated dredged materials, the primary function of the closure is to limit the
infiltration of precipitation and surface water run-on/off into the contaminated materials, A layer can
be made to function as a barrier either due to its low permeability relative to the adjacent layers or
as part of a water-balance system that balances infiltration and evapotranspiration. The design of
the barrier layer must provide the following:
A cover with a permeability less than or equal to that of the liner system placed
beneath the dredged materials. This is to prevent a long-term buildup of water within
the waste. Note that water-balance systems are not evaluated using this criteria
since their performance is more related to vegetation induced evapotranspiration.
121
-------
LANDFILL CHARACTERISTICS
REMEDIAL OBJECTIVES
COVER TYPE
Minimal Hazardous Substances in
Landfill and Minimal Contamination
ol Groundwater
Significant Percentage of Hazardous1
Substances in Fill Are Below the
Water Table. And Lowering the
Water Table Is not Practicable
Leaching of Hazardous Substances
to Groundwater Is Expected to
Contribute to Unacceptable Human
Health or Environmental Risks.
Reliability of Single Barrier Is
Considered Adequate,6 and
Potential/Actual Landfill Gas
Emissions
(Prevent Direct Contact?
Minimize Erosion a
c
Native Soil Cover
Prevent Direct Contact;
Minimize Erosion;
Minimize Infiltration;
Control Landfill Gas
Emissions
C
Single-Barrier Cap b
Significant Contaminant Mass
in Fill, and Risks ol Hazardous
Substances Leaching to
Groundwaler Are Great
Prevent Direct Contact;
Minimize Erosion;
Prevent Infiltration;
Control Landfill Gas
Emissions
Composite-Barrier Cap
High Degree ol Reliability Needed
I in Method of Minimizing Leaching
I of Hazardous Substances to
I Groundwatar and Controlling
I Landfill Gas Emissions i
Primary objective is lo prevent direct contact, although the soil cover can be designed to roduco infiltration.
Single-barrier caps may include additional layers that provide protection to that barrier.
c Examples include situations where infiltration is not the orimary concern and may include sites containing a
small volume of contaminant mass, regions with low annual precipitation, or sites where groundwater is not
being used as a source of drinking water.
(EPA/540/P-91/001;
Figure 7.3 EPA CERCLA Landfill Cover Selection Guide
122
-------
Sufficient flexibility in the cover system to accommodate long-term settlements of the
dredged materials.
A design life that exceeds the projected life of the mobile contaminants.
Design considerations for barrier layers are presented in this section.
Permeability Barrier Low permeability barrier layers are typically constructed using compacted
clay layers, geomembranes, geosynthetic clay layers, or a composite barrier consisting of a
geomembrane over a compacted clay layer. The flow of water through a well constructed clay
barrier is controlled by the permeability of the clay and the hydraulic gradient acting on the clay
(Darcy's Law). Reduction in infiltration through this clay barrier requires either 1) reducing the
permeability of the clay with admixtures or 2) reducing the hydraulic gradient by decreasing the
height of water standing on the barrier or increasing the barrier thickness. Compacted clay layers
must be protected against both desiccation and freezing to maintain their low permeability (Zimmie,
1990). In Region 5, this can require a minimum of 4 feet of soil cover over the clay barrier.
Flow through a geomembrane cover can be by diffusion of the liquid through the liner (Pick's First
Law) or flow through holes or defects in the membrane. For most geomembranes, the rate of
diffusion of liquids is very low. Significant flow can occur, however, through a hole in the membrane.
Assuming a very permeable layer exists beneath the geomembrane, the flow through a defect in the
geomembrane is given by (Giroud and Bonaparte, 1989) the equation:
,05
Q = CB a (2gh)
where Q is the flow rate (m3/s); CB is the flow coefficient with a value of approximately 0.6; a is the
area (m3) of the hole; g is the acceleration due to gravity (9.81 m/s2); and h is the head (m) of water
over the geomembrane. For example, for a single hole having an area of 1 cm2 (0.0001 m2) acted on
by a 30 cm head, the flow through the hole in a single day is 12,491 liters (3300 gallons).
A composite barrier reduces the flow rate through geomembrane penetrations by backing up the
geomembrane with a low permeable soil layer. The flow through a hole in the geomembrane
reduces to the following equation:
Q = 0.21 h°9a01 ks074
where ks is the permeability of the underlying soil. For the case of the 1 cm2 hole having 30 cm of
head acting on the geomembrane and backed by a soil with a permeability of 1x10'7 cm/sec, the
flow rate reduces to 0.06 liters/day (.016 gal/day). This is a dramatic reduction from the
geomembrane alone.
123
-------
Water-Balance Barrier Infiltration through a water-balance barrier is minimized using a layered
system that limits the penetration depth of infiltration while providing for maximum
evapotranspiration removal of the infiltration. While the performance of the permeability barrier is
wholly dependent upon the integrity of the barrier layer, the long-term performance of the water-
balance system is dependent upon both its initial design and the maintenance of vegetation to
provide evapotranspiration, and the weather. A water-balance cover layer currently proposed for
long-term isolation of mixed wastes is shown on Figure 7.4. The upper layer of the cover is
designed to support vegetation and to provide sufficient hydraulic storage capacity that infiltration
during the wettest season will not saturate the system. The depth of penetration for the infiltration is
limited to the upper layer using a physical phenomena referred to as "Richards Effect". The
"Richards Effect" is due to capillary tension retaining the moisture in the fine grained surface layer.
By placing a coarse grained layer (e.g. coarse sand or gravel) beneath the fine grained surface
layer, infiltration will not move out of the surface layer until the surface layer is saturated and the
surface tension overcome.
The long-term performance of a water-balance cover is therefore dependent upon the following:
Providing sufficient hydraulic storage capacity in the upper layer to store maximum
projected infiltration without saturating the layer;
Planting and maintaining sufficient vegetation on the cover to remove, via
evaportranspiration, moisture held in the upper layer; and
Limiting the depth of infiltration penetration through the Richards Effect.
Stability of the weather pattern.
For CDFs, the upper barrier layer could be constructed using clean, fine-grained dredged materials.
The lower, coarse layer could be constructed using dredged materials composed of coarse sand.
Site specific evaluation of a water-balance cover can be done within Region 5 using the HELP
computer model previously discussed.
Settlement Criteria The barrier layer must be able to conform to settlements of the sediments
and still function. As with settlement criteria of engineered structures, the most significant challenge
to the barrier layer is due to large differential settlements that occur over relatively short lengths. In
conventional landfills the design model for differential settlement might be the development of a void
immediately beneath the cap due to the rusting out of a refrigerator, etc. Large differential
settlements within a CDF are not anticipated unless zones of dredged materials having significantly
different properties are present. An example would be a zone of clam shell excavated sediments
having high unit weights surrounded by low strength and density hydraulic-dredged material.
Normal density gradients associated with hydraulically-placed sediments should not impact the
performance of the barrier layer. An additional zone of potential high differential settlements occurs
124
-------
cn
CLIMATE
PRECIPITATION ,/ / / / //
GRAVEL
ARMORING
TRANSPIRATION ()
L.tf- 4\ &^l i^JF &J
m
WASTE ZONE
Figure 7.4 DOE Water-Balance Cover
-------
at the perimeter of the CDF where the soft compressible sediments are deposited directly against
the containment dikes. If the barrier layer extends over the dikes, then it must bridge large localized
zones of differential settlements that occur between the rigid dikes and the softer dredged material.
Research into allowable differential settlements for barrier layers has been performed by COE for
EPA (Murphy and Gilbert, 1987). Figure 7.5a shows the strain in the barrier elements as a function
of localized differential settlements. Common geomembranes such as high density polyethylene
(HOPE) can tolerate less than 10% of such biaxial strains prior to failure. Compacted soil liners
have an even lower tolerance for strains from differential settlements. Figure 7.5b shows ultimate
tensile strains in soils before formation of cracks verses their plasticity index. The ultimate tensile
strain for typical soil liners prior to failure will be typically less than .25%. Composite liners using a
conventional compacted soil layer are not recommended for zones of high differential settlement.
7.3.2 Surface Water Control Layer Design
Precipitation run-off from the CDF cover must meet water quality standards (see AEPP criteria in
Section 2.2.2) and should not produce excessive erosion of the cover. Each of these two design
criteria require an independent design evaluation.
The water quality of the run-off will be a function of the contaminants available in the sediments and
the partitioning capacity of the water. If field or laboratory tests (Lee, 1991) indicate a water quality
problem due to the contaminants in the sediments, then either the contaminants in the run-off must
be removed, or the contaminants in the dredged material must be chemically fixed (see Appendix
A), or the sediment must be isolated from the run-off by a cover barrier layer.
The surface erosion potential of CDF covers is typically low because of the small slopes associated
with these covers and the reality that the cover is still contained at the perimeter by the CDF dikes.
These geometric constraints for the cover are the result of the initial low shear strength of dredged
materials placed with the CDF. However, the erosion potential is increased due to the silty nature of
much of the dredged materials. Based on criteria developed for RCRA/CERCLA final covers (EPA,
1991 a), the annual soil loss from erosion must be limited to less than 2 tons/acre/vear.
Annual soil loss due to erosion is estimated using the Universal Soil Loss Equation (USLE) given by
A = R K LS C P
where R = Rainfall and Run-Off Index,
K = Soil Erosion Factor,
LS = Slope Constant,
C = Crop Management Factor, and
P = Field Practice Factor.
126
-------
1 00
o.rs
o.so
0.23
Indm of maximum tttttoriMnt A/L v» tcnsto ttram (attw GOb*n and Murony, 1987)
A. Strain vs. Differential Settlement
I I I I I I
3.0
LEGEND
LEONARD I BEAU FLDOIRE TESTS )
O TSCHE30TAH1OFF < DIRECT TENSION TESTS I
Q WCS DATA t DIRECT TENSION TESTS )
FOR THS STUDY (OU OMECT TENSION TESTS)
stnrn ws pteacrty r*** (attw Obart aiM Murony. 1947)
B. Ultimate Strain vs. Plasticity for Clays
Figure 7.5 Soil Barrier Performance
127
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7.3.3 Airborne Emissions Control Design
As discussed in Section 5.3, air borne contaminant emissions from a CDF result from the direct
volatilization of contaminants to the atmosphere and as the result of wind erosion of contaminated
surface sediments. Control of airborne emissions to satisfy the AEPP criteria developed in Section
2.2.7 is required during the interim operational phase of the CDF and during the post-closure life of
the CDF. Such air borne emissions control requires both specific operational practices and design
considerations.
Thibodeaux (Brannon, 1990) identified four primary vapor phase emission pathways related to
dredged materials as follows:
during sediment handling while dredging;
from sediments devoid of vegetation and exposed and drying;
from that portion of the CDF that contains surface water; and
from sediment that is covered with vegetation.
The greatest volatile emissions are thought to occur when the CDF is receiving dredged materials
and when the dredged material is exposed to the air. The volatilization of contaminants occurs prior
to closure of the CDF from dredged materials that are devoid of vegetation, exposed above the
surface water level, and drying. Two operational practices can be used to limit volatilization losses
prior to closure: (1) maintain the surface of the confined dredged material below water, or (2) place a
layer of clean soil or dredged material on the surface of the contaminated material. The selection of
a clean material for use as a volatilization barrier must also consider wind related soil particle loss
(see discussion of PM-1 Os in Section 5.3). It is important to remember that air borne emissions
include both volatilized chemicals and wind blown particulate matter.
From the long-term final cover design perspective, the control of airborne emissions may include
filtering emissions from gas venting systems. The need for a gas venting system in the final cover
must be evaluated for each CDF. In conventional RCRA C and D landfill closures, a gas collection
layer and venting system, see Figure 7.2b, is commonly provided in the final cover to minimize the
build up of gases within the waste. Proposed air quality regulations, see Section 5.3, may require
processing of vented gases to limit the quantity of non-methane organic compounds (NMOC). Such
regulations are focused on MSW landfills that, by the very nature of household wastes, contain
significant quantities of organic materials. Such high levels of organic wastes degrade and even
produce commercially attractive quantities of gas. Dredged materials, however, are primarily
composed of inert solids containing lesser amounts of volatile organics. Additionally, gas venting
systems are used to limit the lateral movement of waste generated gases. Such lateral movements
of gas have posed a significant danger to structures adjacent to landfills. Thus the need for a gas
venting system must consider the gas generating potential of the dredged sediments and the
potential exposure of adjacent structures.
128
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Limiting the long-term wind blown loss of participate matter may require design considerations that
are subtly different than required for water related erosion. The large, flat final covers associated
with CDFs do not promote water run-off erosion but are ideal for wind blown loss of particulate
material. The final cover design must therefore ensure that a healthy vegetated surface layer
survives or must incorporate a surface layer of soil having a grain size distribution that limits wind
blown erosion.
7.3.4 Plant and Animal Uptake Control Design
The need for control of contaminant uptake by plants or animals is dependent upon both the degree
of contamination in the dredged material, operational practices during the active life of the CDF, and
the presence of a barrier layer in the final cover. Plant and animal uptake potentials can be
estimated using the BioConcentration Factors (BCF) discussed in Sections 5.2.1 and 5.2.2 and
presented in Tables 5-1 and 5-2. The acceptable levels of uptake or AEPP can be determined from
Section 2.2.3 for plants and Section 2.2.4 for animals. A dredged material containing a contaminant
that has a high BCF may require measures to be incorporated in operational procedures, and into
the final cover to restrict the exposure of animals via the food chain. Operational measures to
restrict plant and animal uptake may include placing an interim clean layer of dredged material over
the problematic dredged material and the elimination of surface depressions that form ponds. The
effectiveness of a clean buffer layer to limit uptake, e.g. its minimum required thickness, must be
validated using laboratory bioassay tests like those shown on Figures 2-7 and 2-8.
Control of plant uptake of contaminants from CDF sediments can be accomplished by the critical
selection of plant species and/or the control of root penetration. Work by (Lee, C.R. et al, 1991) has
shown that many grasses are selective in their ability to uptake contaminants such that plant uptake
can be limited by correctly matching sediment contaminant presence and availability to plant intake
preference. The long-term success of such an approach, however, is limited by the degree of
invasion by volunteer vegetation. Limiting the growth of trees and grasses with more aggressive
root systems requires long-term maintenance of the cover. Tree growth is best limited by annual
mowing of the cover. Such practices are not commonly part of historical CDF closure plans.
To minimize long-term maintenance requirements, covers need to be designed to limit root
penetration of volunteer trees, large shrubs, and many wild grasses. Root penetration can be
limited by the use of a geomembrane or a herbicide-impregnated geotextile. The geomembrane
provides a simple physical barrier to the roots (and moisture infiltration) at a typical installed cost of
$0.30 to $0.70 per square foot. The herbicide barrier kills the plant to limit root penetration but cost
$2.00 to $2.80 per square foot. Having a service life of less than 20 years and significant cost, the
herbicide barrier may be suitable only for limited applications where water flow must be allowed but
root penetration limited.
Designed control measures to limit animal uptake of contaminants must reflect the level of long-term
maintenance of the cover and the nature of the contaminants. Ponding of water on the interim and
129
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final covers must be prevented to limit a potential chain that can uptake contaminants. In the case
of surface ponds, fish within the ponds readily uptake metals from adjacent sediments and provide a
vehicle for contaminant movement up the food chain. If ponds are proposed on a cover, then a
barrier system could be incorporated between the pond water and the dredged material if
necessary.
Long-term maintenance may require that animals be limited to grazers who do not burrow. The
presence of grazers should be restricted (fencing, etc.) if plant intake of contaminants is possible.
Ongoing work by the Department of Energy ( Landeen, 1990 ) has shown that burrowing animals
can readily penetrate 3-meters into a cover but do not penetrate even flexible geomembranes.
A low permeability layer may be incorporated into the final cover system for other closure objectives,
e.g. to limit infiltration. The presence of a soil or geomembrane low permeable layer in the final
cover will limit the uptake of contaminants by plants or animals by restricting access of roots or
benthic organisms to the dredged materials.
7.4 CDF Final Cover Selection Guide
The final closure objectives and final closure component design considerations previously discussed
in this Section are consolidated to the CDF cover selection guide shown on Figure 7.6. Six
scenarios are used to characterize a CDF based on three criteria: 1 - level of contamination in the
dredged material (minimum(less than problematic) or maximum (problematic)), 2 - the potential for
contamination of the groundwater underlying the CDF. The six CDF characteristics scenarios can
be reduced to four distinct groupings of final closure objectives as shown on Figure 7.6.
Closer examination of the individual final closure objectives shows that they are not independent
objectives. For example, placement of a barrier layer in the cover to limit infiltration will also limit air
emissions and plant or animal uptake. This overlap of closure objectives allows the potential final
cover profiles to be reduce to only three in number. These three cover profiles are shown on Figure
7.6. All three cover profiles incorporate a surface layer of vegetated dredge material to reduce
surface erosion. Such erosion is suspected to be very limited due to the flat topography that
characterizes the placed CDF waste.
Two of the final cover profiles utilize a layer of clean dredged material. In one profile, a clean
dredged sand is used to provide infiltration storage capacity so that the erosion limiting plants will
survive droughts. The thickness of the sand layer is evaluated based on water balance criteria to
ensure the availability of moisture to plants during times of drought. The water balance evaluation
can be performed using EPAs HELP (Hydrologic Evaluation Landfill Performance) computer model.
The remaining clean dredged material cover uses low-permeability dredge material that forms a low
permeability barrier layer to limit infiltration, air emissions, and plant or animal uptake. The
thickness of this layer must be greater than required by any of the criteria.
130
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CDF Characteristics
Closure Objectives
Cover Type (SL and UL)
MINIMUM CONT. IN DM
MINIMUM POTENTIAL CONT. OF GW
MINIMUM CONT. IN DM
MAXIMUM POTENTIAL CONT. OF GW
MINIMUM CONT. IN DM
EXISTING CONT. IN GW
MAXIMUM CONT. IN DM
MINIMUM POTENTIAL CONT. OF GW
MAXIMUM CONT. IN DM
MAXIMUM POTENTIAL CONT. OF GW
MAXIMUM CONT. IN DM
EXISTING CONT. OF GW
EROSION CONTROL] ACETATE DREGE MATERIA!]
EROSION CONTROL
LIMIT INFILTRATION
EROSION CONTROL
VOLATILE EMISSIONS CONTROL
LIMIT ANIMAL/PLAN, UPTAKE
EROSION CONTROL
VOLATILE EMISSIONS CONTROL
LIMIT ANIMAL/PLANT UPTAKE
LIMIT INFILTRATION
VEGETATED DREDGE MATERIAL
OLEAN.GRANULAR DREDGE MATERIAL
BARRIER (GM OR GO.)
AVAILABLE LOW PERMEABILITY
DREDGE MATERIAL?
VEGETATED DREDGE MATERIAL
CLEAN, RNE-GRAJNED DREDGE MATERIAL
Figure 7.6 CDF Cover Selection Guide
CONT = CONTAMINATION
DM = DREDGE MATERIAL
GW = GROUND WATER
(1) THICKNESS DETERMINED BY INFILTRATION OR
UPTAKE CRITERIA
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Unit costs for the components making up three cover profile are estimated as follows:
Vegetative erosion control ($1500/acre) $0.04/ft2
Clean dredged material ($10/ton) $0.50/ft2/ft thickness
Barrier layer (GCLorGM) $0.65/ft2
The total unit costs for the three cover profiles range from $0.04/ft2 for the vegetative cover only, to
$1.04/ft2 for the vegetative cover plus two feet of clean dredged material, to $1,69/ft2 for the latter
plus a geosynthetic barrier layer. The full barrier will increase disposal costs approximately $1.20
per ton (assuming a 20-foot average dredge material thickness).
132
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SECTION 8
OPERATIONAL AND POST-CLOSURE MONITORING
Each of six contaminant pathways discussed in this document may require monitoring during
the actual placement of dredged sediments in the CDF, during the interim between placement
of dredged materials in the operational life of the CDF, or during the post-closure period
required for the CDF to reach an equilibrium state. Recalling from Section 1, the long-term
equilibrium state must reflect potential contaminant partitioning mechanisms and resulting
transport mechanisms. Current monitoring programs tend to be short-term focused and
predicated on the solids retention philosophy of contaminant containment. Such monitoring
programs are appropriate during operations. Post-closure monitoring programs must be able to
detect secondary pathways not related to solids retention. Specific monitoring requirements
will be influenced by the type and degree of contamination, the setting, type of CDF (e.g.
upland, in-lake), the site specific hydrogeology, and the design details of the specific CDF
contaminant system.
Both the operational and post-closure monitoring programs are intended to track and document
the influence of the CDF on the surrounding ecosystem. As such, the effectiveness of these
monitoring systems is predicated on a clear identification of the background environmental
conditions that exist prior to construction of the CDF. Such background ambient site data
includes surface water quality on or adjacent to the site, ground water quality beneath and
down gradient of the site, and air quality at the site.
8.1 Monitoring During Operations
During the actual placement of dredged sediments within the CDF, the potential for
volatilization of contaminants and the loss of free water (or supernatant) are at a maximum.
The specific contaminant pathways that may require monitoring during placement of dredged
sediments include the impact of contaminant volatilization on air quality in the vicinity of the
CDF, and the impact of the free water on effluent quality and site groundwater quality As
discussed in Section 5.3, the level of contaminant volatilization during placement of dredged
sediments is significantly influenced by the dredging process used to dredge the sediments.
For example, hydraulic dredging is commonly preferred at environmentally sensitive dredge
sites because it limits the turbidity resulting from the dredging process. Hydraulic dredging
does, however, fluidize the dredged sediments, resulting in an increased percentage of
sediments in suspension and a significant increase in the quantity of supernatant. At the point
of discharge within the CDF, the contaminants are more mobile so that the potential for
volatilization or advective transport of the contaminants is increased.
133
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As the level of the dredged material rises above the level of the supernatant, the exposed
dredged material becomes exposed to direct sunlight and free oxygen. The resulting heating
and drying of the dredged material can lead to an increase in the volatilization of contaminants.
Additionally, the differential subsidence of the dredged material can produce surface ponds that
support both fish and a benthic community. In this fashion, the interim exposed surface of the
dredged material can foster both plant and animal uptake of contaminants. Monitoring for
potential volatilization and plant or animal uptake is required to determine if an interim cover of
clean dredged material is required to limit contaminant loss.
8.1.1 Effluent Quality Monitoring
Effluent can leave the CDF through a designed weir point discharge system or via seepage
through the perimeter dike. Water quality monitoring of the effluent discharge from the point
discharge system or at the fringe of a mixing zone is conventional and does not require
clarification in this manual. Effluent seepage through the perimeter dikes is more difficult to
monitor because of uncertainties related to potential seepage pathways and the potential
impact of the dike on effluent quality. These factors are discussed in Section 6.1. For
example, the monitoring of seepage through dikes is complicated by dye studies (e.g. Pranger,
1 986) that have shown that seepage in shoreline and in-lake CDFs is not uniform, but rather
occurs at discrete points. Traditional monitoring wells placed within the perimeter dikes can
easily miss such fingers of contaminant flow and therefore do not provide effective monitoring.
The development of discrete plumes leaving the marine dikes can be detected using dye studies
or geophysical techniques such as acoustical echo tracking. This method measures the sonar
backscatter intensity that can be correlated to chemical turbidity concentrations (ref).
Additional monitoring methods can include satellite imaging if the effluent produces sufficient
change in the physical environment at the point of seepage.
8.1.2 Leachate Discharge Monitoring
Downward flow of water-carried contaminants from within the CDF can be detected by the
installation of monitoring wells within the CDF. Such wells will required proper screening and
sealing to prevent direct contamination from the supernatant. Such sealing typically requires
initially placing a conductor casing through the dredged material and into an aquitard beneath
the dredged material. After sealing the conductor casing to the aquitard, the deeper monitoring
well is placed through the conductor casing. Such considerations are clearly reviewed in
existing manuals (see EPA, 1987). Such monitoring wells are easily damaged during operation
of the CDF. Protection of monitoring wells placed within perimeter dike system is conventional
and may simply require use of steel locking caps and traffic barriers. Protection of monitoring
wells placed within the CDF is much more difficult and may require construction of "islands" of
clean dredged sediments, through which the wells are placed, to protect the wells during
placement of dredged sediments or placement of the wells after closure.
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8.1.3 Air Quality Monitoring
At CDF sites where dredged materials are exposed above the waterline, the air quality at the
point of discharge of the dredged sediments may require air quality monitoring for the specific
volatile contaminants present in the dredged sediments. It should be noted that such
monitoring differs from "odor" monitoring in that specific volatile compounds should be
targeted.
8.2 Post-Closure Monitoring
The level of monitoring required after placement of the final cover over the CDF is significantly
influenced by the type of cover used. General guidelines for post-closure monitoring are given
on Table 8.1. In general, the monitoring of contaminant pathways related to effluent and
leachate discharge remain the same as previously developed for the operational conditions.
The influence of the final cover on contaminant pathway control is impacted by both the
contaminant type and the type of barrier system incorporated in the cover as shown on Figure
7.6.
8.2.1 Surface Water Run-Off Monitoring
A monitoring and sampling program should be established for both the water and sediments
carried off the CDF final cover to ensure the cover is a secure barrier. Note that in many CDF
closures the run-off from the final cover is still contained by the perimeter dikes such that a
uncontrolled discharge is avoided. Surface water run-off monitoring is commonly performed on
an annual basis for MSW landfills adjacent to sensitive waters.
8.2.2 Plant Uptake Monitoring
Lacking a secure barrier in the final cover, an annual harvest of surface vegetation should be
performed. This harvest limits the growth of trees and volunteer vegetation that may be deep
rooted and provides vegetation samples for assaying of specific chemical uptake. The
guidelines for the assaying program should be established based on the specific target
contaminants in the dredged sediments.
8.2.3 Animal Uptake Monitoring
Fish and benthic organisms present both immediately outside the CDF and above the final
cover should subject to regular bioassays if a secure contaminant barrier is not designed into
the final cover. The suitability of the final cover to serve as a nesting ground should be
minimized if contaminant transport through the final cover is possible. This may include
removal of surface ponds that form on the final cover and the elimination of vegetation required
for nesting. The development of ponds on the final cover can be inexpensively tracked and
135
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Table 8.1
Monitoring Requirements for Contaminant Pathways
CDF Characteristics
Minimum Cont. in DM
Minimum Potential Cont. of GW
Minimum Cont. in DM
Maximum Potential Cont. of GW
Minimum Cont. in DM
Existing Cont. in GW
Maximum Cont. in DM
Minimum Potential Cont. of GW
Maximum Cont. in DM
Maximum Potential Cont. of GW
Maximum Cont. in DM
Existing Cont. of GW
Contaminant Pathway
Effluent
NR
NR
NR
All-Weir
Discharge WQ
SL,IL-Dike
Seepage WQ
All-Weir Discharge
WQ SL,IL-Dike
Seepage WQ
All-Weir Discharge
WQ SL,IL-Dike
Seepage WQ
Leachate
NR
Minimal
Perimeter
Monitoring
Wells
Extensive
Mrnitoring
Wells**
Minimal
Perimeter
Monitoring
Wells
Extensive
Monitoring
Wells"*
Expanded
Perimeter
Monitoring
Wells*
Surface
Water*
NR
NR
NR
Annual Sampling
of Run-off
Annual Sampling
of Run-off
Annual Sampling
of Run-off
Plant
Uptake*
NR
NR
NR
Annual
Harvest and
Analysis
Annual
Harvest and
Analysis
Annual
Harvest and
Analysis
Animal
Uptake*
NR
NR
NR
Limit Ponding and
Grazing Animals
Limit Ponding and
Grazing Animals
Limit Ponding and
Grazing Animals
Volatilization*
NR
NR
NR
Annual Inspection for
Distressed Vegetation
Annual Inspection for
Distressed Vegetation
Annual Inspection for
Distressed Vegetation
CJ
O)
SL
IL
UL
Shore Line
In Lake
Upland
No Post-Closure Monitoring Required if Geomembrane is Incorporated in Final Cover.
Include Both Interior and Perimeter Monitoring Wells
-------
predicted by the collection and interpretation of colored infrared and thermal infrared imagery
of the CDF cover (Stohr et al, 1 987). This simple technique simply detects vegetation stressed
by saturation of the root zone. Such saturation only occurring within regions of ponding.
Indication of contaminant uptake in plants (Section 8.2.1) should trigger a increased program of
animal uptake monitoring.
8.2.4 Volatilization Monitoring
While it is acknowledged that the maximum rate of volatilization of contaminants occurs during
placement of the dredged sediments into the CDF (See Section 5.3), gases generated by the
dredged sediments could have a detrimental impact on the final cover vegetation. Lacking an
adequate barrier system in the final cover, volatilization of the contaminants can cause the
localized distress of the vegetation at the point of discharge. The presence of distressed
vegetation can be evaluated using the same colored infrared and thermal imagery used to track
the development of ponds. Provisions should be made to install passive gas venting systems if
it is shown that the vegetative distress is related to emission of volatile contaminants.
137
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APPENDIX A
CONTAMINATED SEDIMENT TREATMENT
A.1. Introduction
Treatment of contaminated sediment will usually involve combining several appropriate technologies
into an overall scheme for achieving a cleanup objective. The treatment of dredged contaminated
sediment and subsequent placement in a confined disposal facility (CDF) typically include the
following steps: removal, transport, interim storage, pretreatment, treatment, disposal, and effluent
(including surface runoff) or leachate treatment. In this section the pretreatment and treatment steps
will be discussed. All processes in this chapter were recommended for study in the ARCS program
(Averett et a I.. 1990).
A.2. Soil Chemistry
A.2.1 Properties of Sediments Affecting Contaminants
Sediments requiring remediation can vary widely in terms of physical and chemical properties. The
primary physical characteristic is texture (i.e. the distribution of sand, silt, and clay sized particles).
In general, sandy sediments have little attraction for either toxic metals or synthetic organics
(pesticides and industrial organics). In contrast, fine textured 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 remove contaminants from the water
column. These fine textured materials have large surface areas when compared to either their
volume or mass (e.g. specific surface). This large surface area serves as a site for colloidal
chemistry to occur. These particles tend to accumulate in more quiescent reaches of waterways.
Separation of the less contaminated gravel and sandy fractions from contaminated sediments may
be possible, yielding material clean enough for disposal without restriction, while also reducing the
volume of the contaminated sediment requiring treatment.
A second very important physical property is the organic matter content. Fine textured sediments
generally contain from one to several percent naturally occurring humic material derived from
microbal transformation of plant and animal detritus. Sandy sediments typically have less than one
percent humic material. Humic material may be present as discrete particulates or as coatings on
either clay or fine sandy sediments particles and is important in two respects: (1) the humic material
greatly increases the affinity of sediments for metals (e.g. bind, chelate and complex) and nonpolar
organic contaminants and (2) 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 because it is a measure of the amount of void space present in the sediment
and as a result the density.
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The chemical properties of sediments also greatly affect the mobility and biological availability of
contaminants. Sediment acidity and oxidation/reduction status are two very important chemical
parameters. Strongly acidic (low pH) sediments can in general slow microbial activity and increase
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 different reactions of metals with oxidized and reduced sediment constituents.
Changes in pH and redox potential of contaminated sediments from their initial in-situ condition at a
dredging site to different conditions at a disposal site can substantially affect contaminant
mobilization/immobilization processes. 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.
Clay minerals have a high specific surface and associated electrical charge. Specific surface is
defined as the surface area of a particle divided by either its mass or volume. The electrical charge
on this surface is predominately negative with some positive sites on the ends of the clay mineral.
The charge distribution is created by the atomic lattice structure that makes up the clay mineral.
The behavior of water-cation systems adjacent to this surface can be described by the Gouy-
Chapman theory developed from colloidal chemistry. The distribution of these cations in terms of
distance from the colloid surface is termed the double layer. These cations distribute themselves
along the surface of the clay platlet but are not permanently attached to minerals. The effect of
various parameters on the double layer thickness and resulting soil structures is presented in Table
A-1. The Gouy-Chapman Theory developed an equation for the double layer thickness that can be
expressed as follows:
eKT
SnneV
where t = double layered thickness
e = dielectric constant
k = boltsman constant
T = temperature
n = electrolyte concentration
e = elementary charge
v = cationic valance
The dielectric constant as utilized in the Gouy-Chapman equation is a measure of the pore fluids
ability to act like an insulator and influence the strength of the clay minerals electric field. A
reduction of the clay minerals electric field reduces the thickness of the double layer and hence, the
colloidal clay behavior. As the dielectric constant increases, the thickness of the double layer
increases causing a tendency for particle dispersion and the pore fluid acts more like a polar
molecule. Therefore, if the liquid within the pore spaces is not polar (such as a petroleum product),
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then the diffuse double layer will not develop. A table of typical values of dielectric constant for a
variety of different fluids is presented in Table A-2.
A.2.2 Forms and Reactions of Contaminants
Typical trace and toxic metal contaminants in dredged sediments commonly include copper, zinc,
cadmium, lead, chromium, nickel, arsenic, mercury. These elements 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 concentrations that they pose a potential problem. Toxicity may
be experienced 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 available to most aquatic organisms. Metals
bound to clay minerals and humic material by cation exchange processes are available due to
equilibrium partitioning between these bound metals and dissolved metals. On the opposite
extreme, metals bound within the crystal lattice structure of clay minerals are generally much less
bioavailable.
Metals may be mobilized or immobilized if the chemical environment (e.g. pH and Eh) of the
sediment or dredged material changes. Therefore, understanding the influence of the in-situ
sediment chemical environment, and the potential of alteration in these parameters at the disposal
site are important to the selection of disposal alternatives for contaminanted sediments. The fate of
potentially available metals as sediment conditions change is presented in Table A-3. In addition
there may be a complex 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.
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 associated with the sediment solid phase, particularly the humic 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 contaminants may also be highly associated with
petroleum-based or sewage-based organics.
Unlike metals, however, organic contaminants do degrade. Though all organic contaminants
degrade at some rate, some have half-lives on the order of several decades. Chemical half lives
are measures of persistence, or how long a chemical will ramain in various environmental media.
The half lives are the result of all removal processes (e.g. phase transfer, chemical transformation,
and biological transformation) acting together. A summary of typical half lives of organic
contaminants found in contaminated sediments is presented in Table A-4. Some organics are
subject to enhanced degradation rates under certain sediment chemical conditions.
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A.2.3 Sediment Toxicity Assessment
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. The primary tools include environmental regulations based on bioaccumulating
contaminants and sediment assessment methods. Environmental regulations are the most
important and have previously been covered in Section 1.1 Regulation of Dredging Activity. In the
following sediment assessment methods will be discussed.
Although sediments are an extension of the water column, assessment of sediment toxicity is much
more complex than assessment of water quality. Due to the nature of sediment chemistry, presence
of contaminants does not necessary mean that the sediment is toxic. For example, contaminants
may be present but complexed by humic material in the sediment and thus relatively unavailable.
The EPA has developed a "Sediment Classification Methods Compendium" (EPA, 1991) to serve as
a reference for methods that could be used to assess the quality of contaminated sediments. This
compendium describes the various methods, as well as their advantages, limitations, and existing
applications. The sediment quality assessment methods are presented in Table A.5. 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 toxicological effects become manifest or (2) some
amount of bioaccumulation occurs. The sediment quality assessment methods described can be
classified into two basic types: quantitative or qualitative (refer to Table A.6). Quantitative methods
are chemical-specific and can be used to generate numerical sediment quality values. Descriptive
methods are qualitative and cannot be used alone to generate numerical sediment quality values for
particular chemicals.
Currently, the EPA is working toward the development of nationally applicable sediment quality
criteria (SQC). The SQC represents the best recommendation of sediment contaminant
concentrations that will not unacceptably affect benthic organisms or their uses. SQC would
eventually be developed for each high priority contaminant of concern.
Equibrium partitioning (EqP) theory is the EPA's selected method to establish national SQC. The
EqP approach relies on established water quality criteria to assess sediment toxicity. The first basic
assumption of the EqP approach is that sediment toxicity is correlated to 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
(e.g. organic carbon) are in equilibrium. Therefore, for a given contaminant, if the total sediment
concentration, the concentration, of sorbent(s), and the partitioning coefficient are known, then the
interstitial contaminant concentration can be calculated. The interstitial contaminant concentration
can then be compared to established water quality criteria to assess sediment toxicity. A flow chart
describing the process is presented in Figure A-1.
A-4
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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 compounds. For non-ionic organic
chemicals the methodology requires normalization to organic carbon. For metal contaminants a
methodology has been developed that is basd upon normalization to acid volatile sulfide. A flow
chart describing the process is presented in Figure A-2.
A.3. Pretreatment
Pretreatment technologies prepare dredged material for treatment or disposal. Objectives of
pretreatment processes are largely dependent on the treatment or disposal options following in the
treatment process train. The objectives of this step are usually one or more of the following:
A. To provide a suitable material for further treatment and/or disposal operations;
B. To enhance or accelerate settling of the dredged materials solids;
C. To reduce the water content of the dredged materials solids;
D. To separate coarser, potentially cleaner, solids from the fine-grained, more
contaminated solids (particle classification);
E. To reduce the overall cost for the remedial action.
Pretreatment technology processes include the following: (1) dewatering, (2) particle classification
(separation), and (3) slurry injection.
A.3.1 Dewatering
Dewatering technologies are processes used to reduce the moisture content of slurries or sludges to
expedite the handling and to prepare the material for further treatment or disposal. The water
generated during dewatering generally contains contaminants as well as suspended solids. Types
of dewatering processes include mechanical, evaporative and settling ponds. Dredged material
dewatering has traditionally been accomplished in ponds or CDF's, which rely on a combination of
seepage, drainage, consolidation and evaporation. Evaporative processes by themselves alone are
not considered a viable alternative for use in the Great Lakes region due to the climate. Most
mechanical dewatering processes reduce the moisture of the feed material to a level comparable to
in situ sediment (about 50 percent by weight) and work best on homogeneous waste streams.
Implernentability for dewatering processes other than settling ponds is poor primarily because of the
high processing rates required for most dredging operations. The primary purpose for dewatering to
minimize the loss of leachate through the dikes and bottom of the CDF. A summary of
recommended dewatering techniques for use in the ARCS program (Averett et_aL, 1990) is
presented in Table A-6.
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A.3.2 Particle Classification
Separation by grain size is important in the management of soils and sediments contaminated with
toxic materials since the contaminants tend to sorb primarily onto fine-grain clay and organic matter.
The most appropriate solids separation technology for a given site depends on the volume of
contaminated sediments; composition of the sediments (particle size distribution of the feed);
specific gravity and chemical analysis of the soil; mineralogical composition; characteristics of the
soil; percentage of sand, humus, clay or silt; composition of the organics in each soil fraction;
moisture content; pH; characterization of the contaminants; types of dredging or excavation
equipment employed; site location and site surroundings, (refer to Figure A-3). Particle
classification options include screening processes that depend on size, processes that depend on a
combination of size and density or density alone, and processes that depend on conductive or
magnetic properties of the particles. A summary of recommended particle classification
technologies evaluated by the ARCS program (Averett etal.. 1990) is presented in Table A-7.
A.3.3 Slurry Injection
Slurry injection technologies are used as a pretreatment step either to add chemicals that condition
the sediment for further treatment and/or accelerate the settling of the suspended solids or to
provide nutrients or microbes that will enhance biodegradation of organics. The process involves
the injection of chemicals or microorganisms into the dredged material slurry to take advantage of
the mixing process available in the pipeline from a hydraulic dredge. A summary of recommended
slurry injection techniques for use in the ARCS program (Averett et al.. 1990) is presented in Table
A-8.
A.4. Treatment
This section discusses the various treatment technologies available for the
decontamination/detoxification of contaminated sediment. Many of the process options are not
stand alone processes, but are components of a system that may involve multiple treatment steps to
address multiple contaminant problems. Specific treatment objectives include the following:
A. Destruction of toxic organic contaminants by conversion to nontoxic end products;
B. Removal of heavy metal or organic contaminants from contaminated dredged material,
thereby concentrating toxic material into a media of smaller volume (extraction), and/or
to reduce the volume of solids for further treatment or disposal;
C. Reduction of the mobility of contaminants in dredged material to a level compatible with
acceptable risks;
D. Compatibility with removal and final disposal options;
E. Compliance with acceptable capital and operating costs;
F. Minimization contamination of other environmental media;
A-6
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G. Avoidance of the addition of potentially toxic materials or the production of toxic
materials during the treatment process.
In addition, most of the processes outlined below will also require one or more pretreatment
processes. A summary of treatment options available for selected contaminants present in CDF's is
presented in Table A-10.
A.4.1 Biological Treatment
Biological degradation technologies use bacteria, fungi, or enzymes to breakdown RGB's,
pesticides, and other organic constituents into less toxic compounds. The micro-organisms may be
indigenous microbes, conventional mutants, or recombinant DNA products. Biological degradation
proceeds with slower reaction rates than thermal or chemical techniques. A summary of
recommended biological techniques evaluated by the ARCS program (Averett etal.. 1990) is
presented in Table A-9.
A.4.2 Chemical Technologies
The objective of chemical processes, such as chelation, oxidation, or reduction, is to change the
form of a toxic material to render it less toxic or to change its solubility, stability, separability, or other
properties affecting handling or disposal. Chemical treatment technologies use chelating agents,
acid or base addition, chlorine displacement, oxidation, or reduction in the destruction,
detoxification, or removal of contaminants found in contaminated sediments. A summary of
recommended chemical technologies reviewed/evaluated by the ARCS program (Averett et al.,
1990) is presented in Table A-10.
A.4.3 Extraction Technologies
Extraction is the removal of a contaminant (organic/inorganic) from soils or sediment by dissolving it
in a fluid that is later recovered and subsequently treated to remove the contaminant or recycled.
Extraction is often used to remove volatile organics from permeable soils and can also be used to
treat soils and sludges contaminated with the following: metals, inorganics, organics (RGB's, TPH,
halogenated solvents, aromatics), amines, ethers, and anilines. Extracting agents that are
employed vary according to the contaminants to be treated. They include water, acids, bases,
complexing and chelating agents, surfactants, and certain reducing agents.
There are two basic methodologies employed utilizing extraction processes. These methodologies
are the following: (1) containerized extraction, and (2) in situ extraction. In the containerized
extraction process soil/sediment is excavated and placed in a container to allow contact with the
extracting liquor. The extracting liquor is then injected into the soil, and contaminants are extracted
from the soil and concentrated in the washing solution. The washing solution leaches the
contaminants out of the soil and is collected and recycled by a specific treatment technology
A-7
-------
appropriate for the type of contaminants involved. For in situ extraction processes, the
contaminated site is typically flooded with an appropriate extraction solution and the elutriate
leaching from the site is collected either by a series of shallow well points or subsurface drains. The
leachate is then treated and recycled back into the site.
A summary of recommended extraction technologies reviewed/evaluated by the ARCS program
(Averett etal.. 1990) is presented in Table A-11. The technologies presented in Table A-12 are the
following: (1) acid leaching, (2) B.E.S.T., (3) C. F. Systems-Propane, (4) Low Energy
(acetone/kerosene), and (5) surfactants.
A.4.4 Immobilization Technologies
The purpose of immobilization technologies is to limit the mobility of contaminants that are present
in sediments. Most immobilization techniques take the form of solidification or stabilization (SIS)
processes performed prior to placement of the dredged material in the CDF. The objectives of S/S
are generally to improve the handling and physical characteristics of the material, decrease the
surface area of the sediment mass across which transfer or loss of contaminants can occur, and/or
limit the solubility of contaminants by pH adjustment or sorption phenomena. Immobilization
techniques are typically used for heavy metal contaminants because they cannot be destroyed and
extraction from soils is a difficult process. Solidification or stabilization is also effective for limiting
the volume of leachate leaving the site. It should be noted that placement of contaminated dredged
material in a low-permeability landfill covered with a low-permeability cap is in itself a physical
immobilization technique. Thus immobilization techniques can include chemical techniques that
modify the dredged materials and containment techniques that simply prevent the movement of
water to or from the waste. A summary of immobilization techniques for use in the ARCS program
(Averett etal.. 1990) is presented in Table A-12.
A.4.5 Thermal Technologies
Thermal technology processes include incineration, pyrolytic, vitrification, supercritical and wet air
oxidation, and other processes that require heating the sediment several hundreds or thousands of
degrees above the ambient temperature. Thermal processes are generally the most effective
options for destroying organic contaminants. Incineration typically achieves destruction/removal
efficiencies greater than 99 percent for organic contaminants. Heavy metals in the incineration
processes generally pass through the process, except that some of the most volatile metals (such
as lead and mercury) can volatilize from the higher temperature processes. Pyrolysis in contrast
involves heating the material in the absence of oxygen. Volatile materials are driven off and
collected or destroyed by secondary processes, and metals, salts, and other nonvolatile materials
melt into molten glass. Vitrification processes use high-voltage graphite electrons to provide the
primary heat source. A summary of thermal techniques reviewed/evaluated by the ARCS program
(Averett etal.. 1990) is presented in Table A-13.
A-8
-------
TABLE A-1
EFFECT OF VARIOUS PARAMETERS ON DOUBLE LAYER
THICKNESS AND RESULTING SOIL STRUCTURES
DOUBLE LAYER
THICKNESS
PARAMETER
INCREASE DECREASE
SOIL STRUCTURE
DISPERSE FLOCCULATED
D
Electrolyte
Concentration
Ion Valence
Dielectric Constant
Temperature
Size of Hydrated Ion
PH
Anion Adsorption
Decrease
Decrease
Increase
High
Large
High
Increase
Increase
Increase
Decrease
Low
Small
Low
Decrease
Decrease
Decrease
Increase
Increase
Increase
Increase
Increase
Increase
Increase
Decrease
Decrease
Decrease
Decrease
Decrease
Note: As shown, a change in any particular parameter (increase or decrease has a related affect on
the double layer thickness and the soil structure.
TABLE A-2
TYPICAL VALUES OF DIELECTRIC CONSTANTS
FOR VARIOUS FLUIDS
CHEMICAL NAME
Cyclohexane
Xylene
Benzene
Aniline
Propanol
Acetone
Ethanol
Methanol
Water
DIELECTRIC
CONSTANT
2
2
2
6
20
22
26
32
80
A-9
-------
Table A-3 - 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
Changes
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
Ref EPA, 1991
A-10
-------
Table A-4 - Half Life Range of Typical Contaminants
Half Life Range in Surface Water (days)
Chemical Name Low
PCBs
acenaphthene
acenaphthylene
anthracene
benzo(a)anthracene
benzo(a)pyrene
benzo(b)fluoranthene
benzo(ghi)perylene
benzo(k)fluoranthene
chrysene
dibenzo(a,h)anthracene
fluoranthene
fluorene
indeno(1,2,3-cd)pyrene
naphthalene
phenanthrene
pyrene
Dieldrin
Chlordane
Vinyl Chloride
chloroform
1 day
1,1,1-Trichloroethane
Carbon Tetrachloride
1 day
Dibromochloromethane
Bromoform
Chlorobenzene
bis(2-Chlorethyl)ether
4-7 days
2-Chlorophenol
1 day
2,4-Dimethylphenol
2,4-Dichlorophenol
Hexachlorocylcopentadiene
2,4,6-Trichlorophenol
20 hours
2-Chloronaphthalene
2,4-Dinitrophenol
2,6-Dinitrotoluene
Benzidine
3,3'-Dichlorobenzidme
0.125
0.10
0.40
1.00
High
12.9
5.00
2.00
2.00
2.1
2.00
Other Half Life
Ranges
0.20
0.02
1.00 .
0.02
0.38
723 days
very persistent
25 minutes
15 months
1
5-9 months
1
274 years
686 years
5.8 hours
1
1
1-day
8-9 days
11 days
1
biomagnified in water
1
no significant microbial degrdation in 64 days
1
greater than 64 days
1
dogs and rats: 68-88 hrs.
long life in soil
blue gill
blue gill
blue gill
blue gill
rat blood
References
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
Note: 1. Reference No. 1, NcNelis, D.N., et al., (1984). Exposure Assessment Methodolgies for Hazardous
Waste Sites", University of Nevada, Las Vegas, Nevada, Environmental Monitoring Systems Laboratory,
Office of Research and Development, Cooperative Agreement No. CR 810550-01.
2. Superfund Public Health Evaluation Manual, EPA 540/1-86/060, Office of Emergency and Remedial
Response, U.S.E.P.A., Washington, D.C.
A-11
-------
TABLE A-5 Sediment Quality Assessment Methods
Type
Method
Numeric Descriptive Combination
Concept
Bulk Sediment Toxicity
Spiked-Sediment
Toxicity
Interstitial Water
Toxicity
Equilibrium Partitioning
Tissue Residue
Freshwater Benthic
immunity 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 lime period, the response of the test
organisms is examined in relation to a specified biological
endpoint.
Dose-response relationships are established by exposing
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 quantity
chemical components responsible for sediment toxicity.
The procedures are implemented in three phases: 1)
characterization of interstitial water toxicity, 2)
Identification of the suspected toxicants, and 3)
confirmation of toxicant identification.
A sediment quality value for a given contaminant is
determined by calculating the sediment concentration of
the contaminant that would correspond to an interstitial
water concentration equivalent to the EPA water quality
criterion for the contaminant.
Safe sediment concentrations of specific chemicals are
established by determining the sediment chemical
concentration that will result in acceptable tissue
residues. Methods to derive unacceptable tissue residue
are based on chronic water quality criteria and
bioconcentration factors, chronic dose response
experiments or field correlations, and human health risk
levels from the consumption of fresh water fish nr
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, sediment toxicity, and
benthic infauna community structure are measured on the
same sediment. Correspondence between sediment
chemistry, toxicity, and biological effects is used to
determine sediment concentrations that discriminate
conditions of minimal, uncertain, and major biological
effect.
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.
Ref. EPA, 1991
A-12
-------
Table A-6 PRETREATMENT COMPONENT DEWATERING
Process Option
Belt Filter Press
Carver-Greenfield
Evaporation
Centrifugation
Treatment Methodology
Belt filter presses use single or double
moving belts to dewater sludges
Consists of three stages. (1)
conditioning by adding of flocculent 0:
thickening drum; (2) gravity drainage
of free water, and (3) compression
zone. Compression zone is provided
by the top belt pressing against the
bottom bel* which serves as a filter.
A food grade carrier oil is injected into
the waste as a fluidizing agent to
maintain the liquid phase as solids
content increases. Oil-soluble
contaminants are extracted from the
waste by the carrier oil, and volatile
compounds are stripped out and
condensed with the carrier oil and
water. Water is removed by thermal
treatment. The carrier oil is removed
by evaporation and stream stripping,
and the contaminants are removed for
distillation. Useful for sediments and
wastes containing oil-soluble
contaminants such as PCB's, dioxins
Technology that uses rapid rotation of
a fluid mixture inside a rigid vessel to
separate the components based on
their mass. Types are solid bowl,
basket and disc Concentrates
soil/sediments from fine gravel to silt.
Factors Controlling
Pprfnrmanrp
r wi t\ji iiiciiiwG
Sediment solids feed
concentration,
flocculent, amount of
pressure between
rollers, filter opening
size
Temperature, carrier
oil
Particle size;
efficiency drops
drastically for
particles smaller than
10 microns.
Minimum Input
Slurry Range
(% solids by wt.)
1-40
8
-
Disc = 1
Output Slurry
Range
(% solids by wt.)
50-60
Solid basket = 15-40
Basket = 9-25
Disc = 6
Cost
Capital cost for
500,000 yd3 facility
$6 million; operation
and maintenance
$20-$100peryd3
Capital cost for 50
Ib/hr dry $500,000.
Operation and
maintenance
$20 to $100 per
yd3.
A-13
-------
Table A-6 (Continued)
Process Option
Chamber Filtration
Gravity Thickening
Primary Settling
(CDF)
Subsurface
Drainage (CDF)
Treatment Methodology
Utilizes rigid individual filtration
chambers operated in parallel under
high pressure to dewater a slurry.
Used in situations requiring a large
area of filtration in minimal area
Operates on differences in specific
gravity between solids and water to
accomplish separation. Process
accomplished in circular vessel similar
to a conventional clarifier.
CDF functions like large settling pona.
Effective settling area reduced by
wind, turbulence and short circuiting.
System consists of a network of
perforated pipes or filter material
placed under or around the perimeter
of a CDF. These pipes or filter
material drain to a series of sumps
where water is withdrawn.
Factors Controlling
Performance
Pressure plate
warpage and
deterioration of plate
gasket.
Maximum flow, waste
type, volume of solids
per day, percent
solids, specific
gravity, surface
chemistry, maximum
particle size, percent
solids required in the
underflow.
Efficiency controlled
by hydraulic
characteristics of the
settling pond and
drainage mechanism.
Permeability of
dredge and filter
material, time.
Minimum Input
Slurry Range
(% solids by wt.)
Output Slurry
Range
(% solids by wt.)
>50
Approximately 50
Cost
Operation and
maintenance cost
$20to$100/yd3
Operation and
maintenance $20 to
$100 per yd3
Operation and
maintenance less
than $20 per yd3
Operation and
maintenance less
than $20 per yd3
A-14
-------
Table A-6 (Continued)
Process Option
Vacuum Filtration
Wick Drains (CDF)
Treatment Methodology
Vacuum filter unit consists of a
rotating cylindrical drum mounted
horizontally and partially submeiged
in trough containing a slurry. A
vacuum supply applies negative
pressure to the inside of the drum
while the moist solids adhere to the
filter.
High permeability polymeric strips to
promote both radial an dvertical
drainage. Normally placed on 5 ft.
centers to depths of 40 ft. Surcharge
used to promote dewatering. Have
been used on CDFs.
Factors Controlling
Performance
Vacuum, degree of
drum submergence,
drum speed, filter
media, porosity, feed
type, solids,
concentration,
chemical
conditioning,
management.
Wick spacing, depth
of CDF, material type,
amount of surchage.
Minimum Input
Slurry Range
(% solids by wt.)
Output Slurry
Range
(% solids by wt.)
20 to 40
Cost
Operation and
maintenance $20 to
$100 per yd3
Operation and
maintenance cost
$20 to $100 per yd3
A-15
-------
Table A-7 - PRETREATMENT PARTICLE CLASSIFICATION TECHNOLOGIES
Process Option
Flotation
Grizzlies
Hydraulic
Classifiers
Size of
Particle
Handled
Fines
Debris to
Gravel
> 1.0 in.
Gravel to
fine sand
Treatment Methodology
Physiochemical process to
concentrate contaminants.
Material is ground finer than
48 to 65 mesh so that the
contaminants will be able to
be floated by air bubbles.
After grinding suspended
particles are treated with
chemicals to cause the
particles to be air-avid and
water repellent. The
mixture is agitated with air
and the contaminants
attached to the air bubbles
float to the surface, forming
froth. This concentrated
froth is skimmed off leaving
a clean product.
Vibrating or fixed separation
units used to remove
oversized matrial and reduce
slurry velocity prior to
subsequent processing.
Physical separation and
classification by grain size
of sand and gravel from
fines by settling velocity
through water.
Equipment
Requirements
Mechanical flotation
device uses an upright
impeller for agitation
and aeration.
Pneumatic device uses
air blowers.
Device consists of
parallel frame mounted
bars spaced 1 to 5 in.
apart. Units can be
used in series or
parallel.
Typically V-shaped
rectangular trough or
cone in which slurry of
a dredge material is
directed. Sand and
gravel particles fall to
bottom and are
recovered through
discharge valves while
fine-grained material is
carried off by water
flow.
Advantages
Corrosion resistance
Improves the
reliability and
efficiency of
separation
technologies.
Maintenance costs
minimal.
Units typically
designed for mobile
system application
with quick startup
and shutdown time.
Fairly simple
maintenance
requirements
Limitations
Dependent upon surface
chemistry, particles size,
shape distribution of
feed, contaminant
distribution with particle
size, characteristic of the
soil, specific gravity and
chemical analysis of the
soil, mineralogical
analysis, solids to liquids
ratio, pH.
None.
Removal and
classification of solids
from 3/8 in. to approx.
74 microns. Some fines
will be removed with
sand and gravel
Size
Requirement
Typically 6 to 9
ft. wide and 12
to 18 ft. long.
Cost
Capital cost $24K to
$160K. Operation
and Maintenance
$20 to $100 yd2
Operation and
maintenance cost
less than $20 per
yd3
Capital cost varies
with size and
capacity. Typical
range $30K to
$76K. Operation
and maintenance
$20 to $100 per yd3
A-16
-------
Table A-7 - PRETREATMENT PARTICLE CLASSIFICATION TECHNOLOGIES (Continued)
Process Option
Hydrocyclones
Impoundment
Basins
Magnetic/
Electrostatic
Moving screens
Size of
Particle
Handled
Separates
clay/silt from
coarser
particles
Gravel to
fine silt
100 micron
or less
1/8 in. to 6
in.
Treatment Methodology
Separates solids (gravels
and sands) from slurry by
vortex-generated
centrifugal forces.
Physical separation and
classification by grain size
of gravel to fine silt by
settling velocity through
water
Separates slurry based on
difference in magnetic and
conductive properties
between contaminant and
the soil.
Plain screening surface in a
rectangular frame.
Typically nested from
coarse to fine at a slope of
20 degrees to allow for a
cascading effect. Screens
may be vibrated, revolving
or gyrated. Vibrated most
common.
Equipment
Requirements
Cone-shaped vessel
with tangential feed
inlet at top. Discharge
pipe located short
distance into vessel to
form vortex.
Diked area or CDF
Slurry is forced through
magnetized steel wool
containing 95% void
space. Intensity of the
magnetic field can vary
from 1 to 100
kilogauss.
Vibrated rectangular
framed screen arranged
in nest. Usually placed
at 20 degrees slope to
allow par'icles to
cascade from one
screen ti the next.
Advantages
Applicable to sites
with limited space.
Wide variety of sizes
and can be operated
in series or parallel.
Handles large
dredging operations
Soils may be dry or in
slurry form.
Can typically handle
300 to 950 tons of
material per hour.
Limitations
Not effective with highly
viscous, high-clay content
slurries, slurries with solids
concentration greater than
30% or particles with
specific gravity of approx.
2.5 to 3.2.
Requires large area. No
solids removal system.
Needs backhoe or
clamshell dredge. Minimal
control when used
employed as a particle
separator
Particles have to be less
than 100 micron in size. If
contaminants finely
disseminated throughout
soil unlikely to work.
Soil has to be dry or
washed through screen
with water. Screen
replacement frequent.
Size
Requirement
Small size
Large area
3 to 10 ft wide
and 6 to 30 ft
long.
Cost
Capital cost varies
according to size and
number. Typical
range $1K - $5K.
Operation and
Maintenance less
than $20 per yd3.
Operation and
Maintenance less
than $20 per yd3
Operation and
Maintenance $20 to
$100 yd3
Capital cost for
screen 10' long, 5'
wide, 5' deep with a
capacity of 200
ton/hr approx. $25K.
Operation and
Maintenance cost
$20 to $100 per
yd3.
A-17
-------
Table A-7 - PRETREATMENT PARTICLE CLASSIFICATION TECHNOLOGIES (Continued)
Process Option
Shaking Table
Spiral Classifiers
Stationary
Screens
Size of
Particle
Handled
Wide range
from slimes
to rocks
Sand and
gravels up to
3/8 in.
Separates
fines from
sands and
gravels.
Treatment Methodology
Feed enters a long upper
edge of table. Wash water
and shaking action spread
the feeJ over the table.
Particles are sorted
according to size by the
arrangement of riffles that
decrease in height along
their length toward the
discharge end.
Settled solids are fed from
the hydraulic classifier into
the spiral classifier by a
rotating screw placed on
an incline. Fines carried to
bottom of incline while
sand and gravel carred up
incline by screw.
The screen surface is
continuously curved. A
slurry is passed over the
screen with a velocity high
enough to produce a
centrifugal force to keep
the slurry in the contact
with the screen.
Equipment
Requirements
Rectangular table with
a slope of 0 to 6
degrees. Surface is
smooth with riffles.
Table capable of being
shaken.
Rotating screws
mounted in an inclined
rectangular vessel with
capability of washing,
dewatering, and
sediment. Require
pretreatment by
hydraulic classifier.
A curved screen
surface. The screen
consist of frame
mounted parallel bars
spaced close together
for a finer particle
separation. A
pressurized water spray
can be added to
increase efficiency.
Advantages
Versatile gravity
separation.
Removes clay and silt
adhering to sand and
gravel. Designed for
mobile systems.
Capable of
processing up to 950
tons per hour.
No more moving
parts; wedge bar
screen is more
resistant to abrasion.
Limitations
Less efficient than
vibrating screen.
Size
Requirement
Typically 22 to
34 feet long, 8
to 1 9 feet wide
and 8 to 12 feet
deep.
Small size.
Cost
Operation and
Maintenance cost
$20 to $100 per
yd3.
$14Kto $77Kfor
single screw; $37K
to $150K for double
screw. Operation
and Maintenance
cost range from $20
to $100 per yd3.
Operation and
Maintenance $20 to
$100 per yd3.
A-18
-------
TABLE A-8 - PRETREATMENT - SLURRY INJECTION
Process Option
Chemical Clarification
Microbe Addition
Size of Particle
Handled
Silt and clays
Silt and clays
Treatment Methodology
Ust of conditioners to promote
coagulation or flocculation of
the smaller size colloidal size
particles. Process increases
rate of sedimentation.
Coagulants include inorganic
chemicals (salts of iron and
aluminum), and organic
polyelectrolytes.
Polyelectrolytes recommended
for dredged material.
Use of microorganisms th it
are acclimated to degrade
toxic materials.
Microorganisms are injected
into pipeline slurry, mixing
them through the sediment
mass.
Equipment
Requirement
Pipeline transport of
dredged material
slurry required to
mix conditioner to
mix conditioner.
Method to inject
conditioner required.
Pipeline transport of
dredged material
slurry required to
mix microorganisms.
Method to inject
microorganisms
required.
Advantages
Polyelectrolytes are
less dependent on pH
and require lower
dosages compared to
inorganic chemicals.
_
Limitations
Settling process required
after injection of
conditioners. Prolonged
periods of mixing reduce
effectiveness.
Different microorganisms
required for different
types of toxics.
Costs
Operation and
maintenance less
than $20 per yd3.
Operation and
maintenance $20
to $100 per yd3
A-19
-------
TABLE A-9 - CONTAMINANT SEDIMENT TREATMENT/BIOLOGICAL
Process
Aerobic
Bioreclamation
Anaerobic
Bioreclamation
Bioreactors
Applicable
Contaminants
Organic materials
Organic contaminants
such as halogenated
compounds, various
aromatics, some
pesticides.
Organic materials
Mechanism
Microorganism are
encouraged to grow in an
aerobic environment
utilizing the organic
contaminant as s source
of food.
Process uses anaerobic
metabolism that includes
anaerobic respiration
using nitrate or sulfate ns
a terminal electron
acceptor and fermenting
methanogenic processes
using a methanogenic
consortium (strictly
anaerobic bacteria).
An aerobic
biodegradation
technology that functions
to increase the
availability of
contaminants and
nutrients to microbes
within a tank. Slurry n
dewatered and resulte it
water treated, if
neceisary.
Factors Affecting
Nutrients for growth of
microorganisms,
oxygen, temperature.
soil moisture, pH.
Temperature, redox
potential of
-250 mv or less, no
oxygen, nitrates or
sulfates can be present.
Nutrients, oxygen, pH.
Demonstrated for
Remediation of
Sediments
Bench
Bench
No
Typical Cost
Operation and
maintenance $20
to $100 per yd3
Operation and
maintenance $20
to $100 per yd3.
Operation and
maintenance $20
to $100 per yd3.
Comments
Methodology can be
used to treat soils and
groundwater
contaminated with
organic materials
Process is slower and
fewer compounds can
be degraded in
comparison to aerobic
bioreclamation.
Limitations of
technology include
inhibition of microbial
metabolism by
chloride substitution
and heavy metals,
and temperatures
outside the optimum
range.
A-25
-------
TABLE A 10- CONTAMINANT SEDIMENT TREATMENT/CHEMICAL
Process
Chelation
Nucleophilic
Substitution
Oxidation of
Organics
Applicable
Contaminants
Metals
RGB's, acids, oils,
thiols, dioxins,
chlorobenzenes.
Oxidation organics such
as aldehydes, phenols
and benzidine. Limited
applications for slurries,
tar and sludge.
Mechanism
Chelating molecule
(ligand) forms multiple
bonds with metal ions
resulting in a heterocyclic
(ringed) structure. The
chelating agents either
increase metal mobility for
removal or immobilize by
sorbing onto clay
materials.
Chemically removes
chlorine from organic
(aromatic) compounds
using the electron donator
principle.
Oxidation state of atom is
increased by removal of
electrons. Oxidation
transforms, degrades or
immobilizes contaminants
in the soil system.
Factors Affecting
pH, chelate dosage,
chelating agent, type of
metal.
Requires alkaline
conditions, (high pH
level, temperature,
reaction time, reagent
dose, moisture content.
Oxidant concentration,
pH, oxidation potential.
Demonstrated
for Remediation of
Sediments
No
Yes
Yes
Cost
Operation and
maintenance of $100
to $200 per yd3.
Operation and
maintenance $150 to
$200 per yd3.
Operation and
maintenance $150 to
$200 per yd3.
Comments
Chelating agents must
be used according to
their affinity for
particular metals.
Two primary processes:
APEG, alkali metal
hydroxides in
polyethylene glycol:
KPEG, potassium -
polyethylene glycol.
Toxic products may form
if reaction is not
complete. Process is not
applicable for high
strength complex waste
systems, nor highly
halogenic organics.
Methodology can be
employed in situ.
A-26
-------
TABLE A-11 - CONTAMINANT SEDIMENT TREATMENT/EXTRACTION
Process
Acid Leaching
B.E.S.T. (Basic
Extraction Sludge
Treatment)
C.F. Systems -
Propane
Low-Energy
Acetone -
Kerosene
Applicable
Contaminants
Metals, amines,
anilines, ethers,
phenols.
PCB's oils, creosote
PCB's and organics.
PCB's and organics.
Mechanism
Steam and/or weak acids such as
aqueous solutions of sulfunc,
hydrochloric, nitric, phosphoric and
carbonic acid are used as dissolving
agents for basic metal salts, amines,
anilines and ethers processes. In situ
treatment may be performed using
weak acid solutions ^uch as acetic
acid and sodium hudrogen phosphate.
Basic solut ons such as NaOH are
used as flushing agents for soils
contaminated with metals such as
zinc, tin, lead and phenols.
Mixture of one part free water
sediment and 1 to 7 parts amine-
based solved, usually triethylamine
(TEA). A single liquid phase forms
and solid matter is removed by
centrifugation and dried to remove
residual TEA. TEA is then processed
to remove contaminants.
Contaminated sediment is fed to the
top of the extractor and makes
non-reactive contact with condensed
propane solvent flowing up through
the extractor at a pressure of 250
psi. Typically used in a series of
three extractors. Contaminated
propane is fed to a separator where it
is vaporized and recycled by
recompression.
This process separates the sediment
into a liquid and a solid, then leaches
the solid portion with a hydrophilic
solvent (acetone). The acetone is
steam stripped from the sediment.
The PCB's are treated with a
hydrophobic solvent (kerosene).
Factors Affecting
Treatment must be
sealed from atmosphere
and operated under a
nitrogen blanket.
Temperature must be
below critical solution
temperature. Alkaline
conditions (pH 10) are
required.
Propane, pressure,
temperature.
Water content > 50
percent.
Remediation of
Sediments, Dredged
Materials
Pilot, No
Demonstrated, Bench
Pilot/Pilot
Conceptual, Bench
Typical Cost
Operation and
maintenance $63
to $200 per yd3.
Operation and
maintenance $60
to $300 per yd3.
Operation and
maintenance $100
to $200 per yd3.
Operation and
maintenance $41
to $200 per yd3.
Comments
A-27
-------
TABLE A-1 1 - CONTAMINANT SEDIMENT TREATMENT/EXTRACTION (Continued)
Process
Surfactants
Applicable
Contaminants
Hydrophobia
organics, non-soluble
organics (RGB's,
crude oil, tertiary
oils).
Mechanism
Surfactants are injected into the soil
to flush contaminants. Typically use
mixture of anionic and nonanionic
surfactants.
Factors Affecting
Remediation of
Sediments, Dredged
Materials
Demonstrated, No.
Typical Cost
Operation and
maintanance $100
to $200 per yd3.
Comments
Field and laboratory
have exhibited
mixed results.
A-28
-------
TABLE A 12 - CONTAMINANT SEDIMENT TREATMENT/IMMOBILIZATION
Process
Chloranan
Encapsulation
In Situ
Encapsulation
Lime-Based
Pozzolan
Portland
Cement - Based
Proprietary
Processes
Applicable
Contsminsnts
Organic compounds,
heavy metals, oil and
grease.
Organic and inorganic
materials such as
metals, esticides,
phenols and PCB's.
Organics and low
levels of metals.
Arsenic, lead, zinc,
copper, cadmium,
nickel, PCB's.
Typically metals and
higher molecular
weight organics.
Mechanism
Process involves the injection of cement,
water and an additive chloranan into
contaminated solids or sludges.
Chloranan encapsulates the organic
contaminants to prevent their
interference with the solidification
process. Contaminants are immobilized
from soils in a concrete-like matrix that's
leach resistant.
Process involving injection and/or mixing
of solidification/stabilization reagents
with contaminated material. Mixing can
be accomplished using agricultural
spreaders and tillers, special augers,
backhoes or clamshells.
Contaminated materials are mixed with a
carefully selected reactive, pozzolanic
additive (typically bituminous coal fly
ash) to a pasty consistency and
subsequently blended with hydrated lime
to form a solid mass.
Portland cement is added as a binding
agent along with a pozzolanic product
(fly ash) to react with any free calcium
hydroxide and thus improve the strength,
handling characteristics, and chemical
resistance of stabilized sediment.
A proprietary reagent is typically mixed
with contaminant, then com'jined with a
cement product to form a st 'bilized
mass. There are a large number of these
types of processes on the market.
Factors Affecting
Water content, type
of solid/slurry
density of soil.
Type of material,
contaminant and
reagent. Water
content.
Type of
contaminant, water
content.
Type of
contaminant, soil
type, reagent type.
Remediation of
Sediments,
Dredged Materials
Demonstrated, No
Demonstrated, No
Demonstrated,
bench scale
testing for
dredged material
Demonstrated,
bench scale
testing for
dredged material
Demonstrated,
bench scale
testing for
dredged material
Typical Cost
Operation and
maintenance $100
to $200 per yd3.
Operation and
maintenance $100
to $200 per yd3.
Operation and
maintenance $100
to $200 per yd3.
Operation and
maintenance $100
to $200 per yd.
Operation and
maintenance $100
to $200 per yd.
Comments
Process only tolerates
low levels of mercury
and moderate levels of
lead. Greater teachability
than cement-based
processes.
Cement reduces the
mobility of heavy metals
due to their conversion
to insoluble hydroxides
or carbonates because of
the elevated pH of
cement. Other sorbents
are added to improve
characteristics.
A-29
-------
TABLE A-12 - CONTAMINANT SEDIMENT TREATMENT/IMMOBILIZATION (Continued)
Process
Sorption
Applicable
Contaminants
Organic and
inorganics.
Mechanism
Process typically involves adding a solids
material to soak up the free liquid in a
soil or waste to produce a product that is
easier to handle. Sorbents include
natural materials such as fly ash, kiln
dust, vermiculite and bentonite, as well
as synthetic materials such as activated
carbon, resins, Hazorb, Locksorb, etc.
Factors Affecting
Quantity of sorbent
for removal of liquid
varies according to
the nature of the
liquid, solids content
of the waste and
chemical reactions
that may occur.
Remediation of
Sediments,
Dredged Materials
Demonstrated, No
Typical Cost
Operation and
maintenance $100
to $200 per yd.
Comments
Sorbents are inexpensive
and plentiful, but are
often required in large
amounts, producing a
problem of disposal.
A-30
-------
TABLE A 13 - CONTAMINANT SEDIMENT TREATMENT/THERMAL
Process
Advanced Electric
Reactor
Circulating Bed
Combustor
Eco-Logic
Fluidized-Bed
Incineration
Applicable
Contaminants
PCBs, dioxms,
heavily halogenated
organics, nerve gas
Halogenated,
nonhalogenated
hydrocarbons.
Chlorinated wastes,
organic wastes
containing PCBs,
halogenated
benzend, phenols.
cycloalkane,
alkanes, d(oxin,
dibenzofuran.
Halogenated and
nonhalogenated
organics, phenols,
methyl
methacrylate, oil
refinery wastes.
Mechanism
Unit consists of a vessel with a
porous carbon core surrounded by
carbon electrides. A radiation heat
shield surrounds the core and
electrodes. Nitrogen acts as a
gaseous blanket that that isolates the
reactants from the core and also acts
as a heat transfer medium between
the carbon electrodes and porous
core. Two post reactor zones are
connected in series.
Process uses high air velocity to
circulate solids and create a larger
and more agitated combustion zone.
Dry limestone is added to feed
material to react with the aci i gas so
that a wet scrubber is not necessar'.
Thermochemical destruction process
that relies on the ability of hydrogen
to dechlorinate organic compounds at
high temperatures.
Process consists of a cylindrical.
vertical, refractory-lined vessel that
contains an inert granular material,
usually sand, on a perforated metal
plate. Combustion air is introduced
at the bottom of the incinerator and
bubbles through the inert bedding
material, causing the bedding
material to become fluidized an
agitated. The waste is pumped into
the vessel and is combusted within
the bubbling material.
Factors Affecting
Temperature,
residence time
Temperature,
residence time
Temperature,
residence time
Temperature,
residence time
Remediation of
Sediments,
Dredged Materials
Pilot/No
Demonstrated, yes
Pilot/Pilot
Demonstrated, No
Typical Cost
Operation and
maintenance greater
than $200 per yd3.
Operation and
maintenance $100
to $200 per yd3.
Operation and
maintenance $100
to $200 per yd3.
Operation and
maintenance greater
than $200 per yd3.
Comments
Transfers energy to the
waste through radiation.
Uses relatively low
temperatures, 1600°F, due
to the high degree of
turbulence.
Mobile unit
A-31
-------
TABLE A-13- CONTAMINANT SEDIMENT TREATMENT/THERMAL (Continued)
Process
High Temperature
Slag Incineration
Infrared
incineration
In-Situ
Vitrification
Low Temperature
Thermal Stripping
Applicable
Contaminants
Waste including low
level radioactive
wastes and most
stable chlorinated
aromatics.
Halogenated and
nonhalogenated
organics, dioxins,
spent activated
carbon.
Organics, inorganics,
heavy metals, PCBs
Volatile organics and
PCBs
Mechanism
Process transforms waste into a
mechanically strong and chemically
stable basalt like material in granular
or bulk form. A homogenous waste
stream is fed into a combustion
chamber. A burner then heats the
top of the waste into a layer of
molten slag. The slag droplets flow
to a granulator where they are
quenched, causing them to burst into
granules.
Waste is prepared to the consistency
and size required. Feed is then fed
on a wire mesh conveyor belt into
infrared primary chamber. Material is
stirred gently by rotary rakes, or cake
breakers.
Process converts waste into a
chemically inert and stable glass and
crystalline product. Mechanism
involves placing 4 large electrodes
vertically inserted in a square
arrangement in the soil. Graphite is
placed on the surface to complete
the circuit between electrodes.
Sand, glass frit, or soda ash can be
added to the soil to improve process.
Combustion gases need to be
processed.
Only enough heat is Applied o
volatize contaminants.
Factors Affecting
Temperature,
residence time
Temperature,
residence time,
waste layer
thickness.
combustion air
flow rate.
Current, electrode
spacing, water
content.
Remediation of
Sediments,
Dredged Materials
Demonstrated, No
Pilot, No
Pilot, Bench
Typical Cost
Operation and
maintenance greater
than $200 per yd3.
Operation and
maintenance greater
than S200 per yd3.
Operation and
maintenance greater
than $200 per yd3.
Comments
A-32
-------
Assumptions
1 Non-ionic organic contaminants only.
2. Sorption of the chemical to sediments can be related to a limited number of sorption phases
and the sorption reaction(s) is (are) fully reversible under natural conditions.
3. Sorption reaction is at or close to equilibrium.
Predict concentration of
contamination in interstitial
water (Cw) knowing
concentration of
contaminant in sediment
(Csed)
Cw =
Csed
Bioavailability of a
contaminant in interstitial
water causes the toxicity to
the organism
Csed
Cw =
For fraction organic carbon (foc)
>0.5% then partition coefficient
K = fo
Predicted Interstitial
Concentration, Cw
Koc partition coefficient of organic
carbon: water
yes
Exceed Water Quality Criteria
no
Sediment Not
Toxic
Figure A-1 - Summary of EPA's -- EqP Model For Estimating Toxicity Of Non-Ionic Organic Chemicals in Sediments
A-33
-------
Function of Mobility in
Pore Water
Biological Response of
Organism
100
Mortality
umol Cd/umol AVS
(solid)
Anaerobic Freshwater
Sediments
Toxicity of Chemicals in
Sediments Strongly Influenced by
the extent to which the chemicals
bind to the sediments
Divalent Metal Activity
Acid Volatile Sulflde (ABC) the amount of
solid phase sulfide in the sediment that is
soluble in cold acid (HCL)
Figure A-2 - Summary of Acid Volatile Sulfide Method for Determination
of Toxicity of Cadmium in Sediments
A-34
-------
Figure A-3 Physical Separation Technology and Particle Size
(Ref. EPA, 1988)
Physical Atinbuies
[screen blaming
Cvclonps Conns Drums
Size
and
Density
UUracentniugation
Mag Separation
Dry
MngniMic bt'OOfntio'i Dry
Electrostatic
Separation
Elecincal
Conductivity
Froth Flotation
Surface
Activity
Foam & Bubble Fracnonanon
Membrane Technology
ngstroms
icrons
illimeters
1
10"
10"
10
10"
io-§
Ionic Range
10'
10"'
ID'5
103
10"
10
10'
1
10 ]
10s
10
10 '
10'
10 '
10'
'0J
Macromolecular __
Range
Micron
Particle
Range
F.ne
Panicle
Range
10'
10'
10
10'
105
100s
Coarse Particle Range
A-35
-------
APPENDIX B
ENVIRONMENTAL PERFORMANCE
REQUIREMENTS
TABLE B1 Summary of EPA Water Quality Criteria or Lowest Observed Effects Levels Where
Criteria are Absent
TABLE B2 Standards for Contaminant Concentrations in Drinking Water
TABLE B3 Demonstrated Effects of Contaminants on Plants
TABLE B4 Additional Action Levels for Contaminants in Foodstuffs Used by Various Countries
TABLE B5 Action Levels for Various Heavy Metals and Pesticides in Plants and Foodstuffs
REFERENCES
B-1
-------
Table B1
Summary of EPA Water-Quality Criteria or Lowest Observed
N)
Pollutant
Acenaphthalene
Ancenapthene
Acrolein
Acrylonitrile
Aldrin
Aluminum
Ammonia, total
Ammonia, unionized
Analine
Antimony
Arsenic
Arsenic (V)
Arsenic (III)
Asbestos
Barium
Benzene
Benzidine
Beryllium
BHC
Bis-2-chloroethoxy methane
Effect
Priority
Pollutant
(Carcinogen)**
N
Y
Y
Y(Y)
N
N
N
N
Y
N
N
Y(Y)
Y(Y)
N
Y
Y(Y)
Y(Y)
Y
N
Levels Where Criteria are Absent
Type
Fresh Water
Acute
1,700.000*
68.000
7,500.000*
3.000
15.700
0.092
9,000.000*
360.000
850.00*
360.000
5,300.000*
2,500.000*
130.000*
100.000*
(Continued)
Criteria - Concentration, ug/l*
Chronic Acute
520.000* 970.0*
21.000 55.0
2,600.000*
1.3
3.900
0.022
1,600.000*
190.000
48.000* 2,319.0*
190.000 69.00
5,100.0*
5.300*
0.340*
Marine
Chronic
500*
13*
36
700*
An asterisk (*) following a number indicates that the value represents the lowest observed effect level (LOEL); when no asterisk appears, the value
is an established EPA water-quality criterion.
The first letter indicates that the compound is (Y) or is not (N) an EPA priority pollutant; the letter in parentheses designates a known carcinogen (Y)
or a suspected carcinogen (S).
From Leeet al (1991)
-------
Tabk»B2
oiOToaras TOT ixxrcarnnarn uoncentrroons m unraonq water
Parameter, mg/1
(unless otherwise noted)
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Silver
Fluoride
Nitrate (as N)
Endrin
Lindane
Methoxychlor
Toxaphene
2A-D
2,4,5-TP Silvex
Trihalomethanes
Turbidity (JU)
Coliform bacteria membrane
filter test (lb/1 00 ml)
Gross alpha (pCi/1)
Combined Radium 226 and
Radium 228
Beta and photon particle activity
(Mrem/yr)
Sodium
Chloride
Color (units)
Copper
Corrosivity
Foaming agents
Iron
Manganese
Odor (threshold number)
pH (units)
Sulfate
Total dissolved solids
Zinc
Drinking
Federal
0.0500
1.0000
0.0100
0.0500
0.0500
0.0020
0.0100
0.0500
1 .4-2.4000
10.0000
0.0002
0.0040
0.1000
0.0050
0.1000
0.0100
0.1000
1.0000
1.0000
1 5.0000
5.0000
4.0000
Monitor
250.0000
1 5.0000
1 .0000
Noncorrosive
0.5000
0.3000
0.0500
3.0000
6.5-8.5000
250.0000
500.0000
5.0000
Water Standards
State of Washington
0.0500
1.0000
0.0100
0.0500
0.0500
0.0020
0.0100
0.500
1 .4-2.4000
10.0000
0.0002
0.0040
0.1000
0.0050
0.10000
0.0100
0.1000
1 .0000
1.0000
1 5.0000
5.0000
4.0000
250.0000
250.0000
1 5.0000
1 .0000
Noncorrosive
0.5000
0.3000
0.0500
3.0000
6.5-8.5000
250.0000
500.0000
5.0000
From Lee et al (1991)
B-3
-------
Table B3
Demonstrated Effects of Contaminants on Plants
Plant Growth Effect-Contaminant Content, mg/kg leaves
Critical
Contaminant
Arsenic
Boron
Cadmium
Cobalt
Chromium
(III), oxides
Copper
Fluorine
Iron
Manganese
Molybdenum
Nickel
Lead
Selenium
Vanadium
Zinc
Normal *
0.1-1
775
0.1-1
0.01-0.3
0.0-1
3-20
1-5
30-300
15-150
0.1-3.0
0.1-5
2-5
0.1-2
0.1-1
15-150
Content**
10% Yield
Reduction**
25% Yield
Reduction
8
20
15
20
11
200
26
290
Varies
2040
500
50-100
500
Phytotoxic*
3-10
75
5-700
25-100
20
25-40
400-2,000
100
500-1,000
100
10
500-1,500
*
* *
From Chaney (1983).
From Davis, Beckett, and Wollan (1978); Davis and Beckett (1978); Beckett and Davis (1977).
From Chaney et al. (1978).
From Leeet al (1991)
B-4
-------
Table B4
01
Additional Action Levels for Contaminants in Foodstuffs
Source Contaminant
Britain Lead
World Health Lead
Organization (WHO)
Cadmium
Dutch Copper
Dutch (unofficial) Cadmium
European Economic Lead
Community
FDA (as of Sep 82) Mercury
Various
pesticides
MAFF Ministry of Agriculture, Fisheries, and Food
WHO World Health Organization
DMAFCMN Dutch Ministry of Agriculture and Fisheries,
FDA U.S. Federal Drug Administration
Commodity
All foods
Root vegetables
Cereal
Leafy vegetables
Root vegetables
Leafy vegetables
Potatoes, cereal
Animal feed
Single animal feed
Mixed animal feed
Roughage
Single animal feed
Mixed animal feed
Roughage
Wheat seed
Vegetables, grains,
and feeds
Used bv Various Countries
Content, mg/kg References*
1 .00 (fresh wt) MAFF (1972)
0.10 (fresh wt) WHO (1972)
0.10 (fresh wt)
1.20 (fresh wt)
0.05 (fresh wt) WHO (1972)
0. 1 0 (fresh wt)
0.10 (fresh wt)
20.00 (dry wt) DMAFCMN (1973)
0.50 (dry wt) European Community (1 974)
1 .00 (dry wt)
1 .00-2.00
(fresh wt)
10.00 (dry wt) Van Driel, Smilde, and
5.00 (dry wt) Van Luit (1 983)
40.00 (fresh wt)
1.00 (dry wt) FDA (1987)
0.03-0.10
, United Kingdom
Committee on Mineral Nutrition
From Lee etal (1991)
-------
Table B6
Action Levels for Various Heavy Metals and Pesticides in Plants and Foodstuffs
Substance
Aflatoxin
Aldnn and dieldnn
05
Arsenic
Benzene hexachlonde (BHC)
Cadmium
Commodity
Cottonseed meal (non-dairy)
Finished feeds
Brazil nuts
Peanuts
Pistachio nuts
Grain (raw cereal)
Rice (in the husk)
Animal feed
Vegetables
Artichokes
Lettuce and carrots
Fruits
Melons
Non-pulpy black-currant nectar
Fructose
Cocoa powders and dry cocoa-
sugar mixtures
Grain (animal feed)
Grain (hurrun food'
Vegetables
Fruits
Provisional weekly tolerance
intake for humans
Data
1
1
1
1
2
2
1
2
1
2
1
1
3
3
3
Type of
Action Level
300.0000 ppb
20.0000 ppb
20.0000 ppb
20.0000 ppb
20.0000 ppb
0.0200 mg/kg
0.0200 mg/kg
0.0300 ppm
0.1000 mg/kg
0.0500 ppm
0.1000 mg/kg
0.500 ppm
0.1000 ppm
0.2000 mg/kg
1.0000 mg/kg
1.0000 mg/kg
0.0500 ppm
0.0500 ppm
0.5000 ppm
0.5000 ppm
0.0067-
0.0083 mg/kg
body weight
Step
Reference
PRL
T
T
PRL
CPG 7126.33
CPG 7112.07
CPG 7112.02
CPG 7112.08
CPG 7141.01-B.1
CPG 7141.01-B.1
CPG 7141 .01-B.1
CPG 7141.01-B.1
CAC/RS 101-1978
CAC/RS 102-1978
CAC/RS 105-1978
CPG 7141.01-B.2
CPG 7141.01-B.2
CPG 7141.01-B.2
CPG 7141 .01-B.2
(Continued)
Data source:
1
2
Type of limit
CPG -
TT
T
PRL
FDA action levels for poisonous or deleterious substances in human food and animal feed, March 1987.
(1982) Food and Agricultural Organization (FAO)/World Health Organization (WHO) Guide to Codex Maximum Limits for Pesticide
Residues
List of maximum levels recommended for contaminants by the joint FAO/WHO Codex Alimentarius Commission. Joint FAO/WHO food
standards programme Codex Alimentarius Commission CAC/FAL 4-1978.
Compliance policy guidelines
Temporary codex tolerance
Codex tolerance
Practical residue limit
Step - Step in the procedure for the elaboration of Codex Maximum Limits for Pesticide Residue given in the FAO/WHO Guide to CODEX M
Reference - Refers to CPG number
(Sheet 1 of 5)
-------
Table BB (Continued)
Substance
Chlordane
Copper
Crotalaria Seeds
DDT, DDE, and TDE
Endrin
Commodity
Root and tuber vegetables
Sugar beet
Leafy vegetables
Stem vegetables
Legume vegetables
Fruiting vegetables
Citrus fruits
Assorted fruits
Pineapple
Passion fruit
Pome fruit
Stone fruit
Small fruits and berries
Cottonseed oil, crude
Cottonseed oil, edible
Linseed oil, crude
Soya bean oil, crude
Soya bean oil, edible
Grain, animal feed
Nuts
Non-pulpy black-currant nectar
Fructose
Cocoa powders and dry
cocoa-sugar mixtures
Edible acid casein
Edible casemates
Grains and feeds
Grain, animal feed
Grain, human food
Cocoa beans
Vegetables
Fruits
Oilseed mt^l, anin al feed
Cottonseed oil, crude
Cottonseed, oil, edible
L'.iseed oil, crude
Data
Source*
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
2
3
3
3
3
3
1
1
1
1
1
1
1
2
2
2
Action Level
0.30 mg/kg
0.30 mg/kg
0.20 mg/kg
0.20 mg/kg
0.02 mg/kg
0.10 mg/kg
0.02 mg/kg
0.10 mg/kg
0.10 mg/kg
0.10 mg/kg
0.02 mg/kg
0.02 mg/kg
0.10 mg/kg
0.10 mg/kg
0.02 mg/kg
0.50 mg/kg
0.50 mg/kg
0.02 mg/kg
0.10 ppm
0.10 mg/kg
5.00 mg/kg
2.0 mg/kg
50.00 mg/kg
5.00 mg/kg
5.00 mg/kg
Avg of one
whole
seed/pound
0.50 ppm
0.50 ppm
1 .00 ppm
0.05 ppm
0.05 ppm
0.03 ppm
0.10 mg/kg
0.02 mg/kg
0.50 mg/kg
Type of
Limit" *
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
-
..
--
--
--
_.
-
T
T
T
Step
6
g
6
6
9
9
9
6
g
6
g
g
6
g
9
9
9
9
-
..
-
__
-
..
g
g
9
R f
71(1)
71(1)
71(1)
72(1)
CPG 7141.01-B.3
CAC/RS 101-1978
CAC/RS 102-1978
CAC/RS 105-1978
1 8th sessions 1 976
App. VI, CS5/70
18th eaesion-1976
CPG 7126.15
CPG 7141.01-B.5
CPG 7141.01-B.5
CPG 7141.01-B.5
CPG 7141.01-B.7
CPG 7141 .01-B.7
CPG 7141.01-B.7
(Continued)
(Sheet 2 of 5)
-------
Table B5 (Continued)
00
Substance
Endrin (Continued)
Fenthion
Hepthachlor and
heptachlorepoxide
Iron
Commodity
Soya bean oil, cru''e
Soya bean oil, edible
Vegetable oils end fats
N'lts
Root and tuber vegetables
Bulb vegetables
Squash
Leafy vegetables
Brassica leafy vegetables
Legume vegetables
Assorted fruits
Bananas
Stone fruits
Plums
Small fruits and berries
Grapes
Cereal grains
Oilseed
Vegetables
Vegetables
Tomato
Carrot
Sugar beet
Fruits
Fruits
Grain, animal feed
Rice, human food
Raw cereal
Soya bean oil, crude
Soya bean oil, edible
Cottonseed
Non-pulpy black currant nectar
Edible acid casein
Edible casemates
Data
Source*
2
2
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
2
2
2
1
2
1
1
2
2
2
2
3
3
3
Action Level
0.5C mg/kg
0.02 mg/kg
0.30 ppm
0.10 mg/kg
0.10 mg/kg
0.10 mg/kg
0.20 mg/kg
2.00 mg/kg
1 .00 mg/kg
0.10 mg/kg
2.00 mg/kg
1 .00 mg/kg
0.20 mg/kg
0.10 mg/kg
0.20 mg/kg
0.50 mg/kg
0.10 mg/kg
0.10 mg/kg
0.05 mg/kg
0.01 ppm
0.02 mg/kg
0.20 mg/kg
0.05 mg/kg
0.01 ppm
0.01 mg/kg
0.01 ppm
0.03 ppm
0.02 mg/kg
0.50 mg/kg
0.02 mg/kg
0.02 mg/kg
15.00 mg/kg
20.00 mg/kg
50.00 mg/kg
Type of
Limit**
T
T
--
T
TT
TT
TT
TT
TT
TT
TT
TT
TT
TT
TT
TT
TT
TT
PRL
PRL
PRL
PRL
PRL
--
PRL
PRL
PRL
PRL
-.
._
Step
9
9
6
3
3
6
6
6
3
6
3
6
3
3
6
6
6
9
9
9
9
--
9
--
--
9
9
9
--
Reference
CPG-7141.01
72 (1)
JMPR 1977
JMPR 1977
JMPR 1977
JMPR 1977
JMPR 1977
CPG 7141 .01
CPG 7141.01
CPG 7141.01
CPG 7141.01
CAC/RS 101-
App. V., CX
1 8th session-
--
B.7
--
--
-B.9
--
-B.9
--
-B.9
-B.9
--
1978,
5/70
1976
App. VI, CX 5/70
Kelthane (Didofol)
Kepone (Chlordecone)
Animal feed
0.50 ppm
18th session-1976
CPG 7141.01-B.6
CPG 7141.01-B.4
(Continued)
(Sheet 3 of 5)
-------
Table B6 (Continued)
CD
Substance
Lead
Lmdane
Mercury
Methyl alcohol
Nitrosodimethylamine (NDMA)
Commoditv
Non-pulpy black currant nectar
Cocoa powders and d.y
cocoa-eugar mixtures
Edible acid casein
Edible caseinates
Vegetables
Root and tuber vegetables
Leafy vegetables
Brassica vegetables
Stem vegetables
Legume vegetables
Peas
Assorted fruits
Small fruits and berries
Cranberries
Fruits
Grain, anirr.^l feed
Grain, human food
Wneat (pink kernels only)
Provisional tolerable weekly
intake for humans
Imported brandy
Barley malt
Malt beverages
Data
Source*
3
3
3
3
1
2
2
2
2
2
2
2
2
2
1
1
1
1
3
1
1
1
Type of
Action Level Limit"*
0.300 mg/kg
2.0000 mg/kg
2.0000
2.0000
0.5000 ppm
0.0500 mg/kg T
0.2000 mg/kg T
0.5000 mg/kg T
0.6000 mg/kg T
0.1000 mg/kg T
0.1 000 mg/kg T
0.5000 mg/kg T
0.6000 mg/kg T
0.3000 mg/kg T
0.5000 ppm
0.1000 ppm
0.1000 ppm
1 .0000 ppm
0.0050 mg
total
Hg/kg body
weight
0.0033 mg
methylmercury
/kg body
weight
0.3500
percent
10.0000ppb
5.0000 ppb
Step
--
--
-
5
3
3
5
9
5
9
3
5
--
--
--
__
-
Reference
CAC/RS 101-1978
CAC/RS 105-1978
App. V, CS 5/70
18th session
App. VI, CS 5/70
18th session
CPG 7141.01-B.10
JMPR 1975
JMPR 1975
JMPR 1975
JMPR 1975
109 (1)
JMPR 1975
110 (1)
111 15)
CPG 7141.01-B.10
CPG 7141.01-B.10
CPG 7141.01-B.10
CPG 7104.05
CPG 71 19.09
CPG 7104.07
CPG 7101.07
Paralytic shellfish toxin
Polychlorinated biphenyls (PCB's) Red meat fat
3.0000 ppm
21 CFR 109.30 (a)
(9) and 609.30
(a) (9) tolerance
used stayed on
8-24-73 (38 FR
22794)21 CFR
109.6 (d) and
509.6 (d)
(Continued)
(Sheet 4 of 5)
-------
Tabla B5 (Continued)
Substance
Commodity
Tin
Canned fruit cocktail
Canned mature processed peas
Canned tropical fruit salad
Non-pulpy black currant nectar
Data
Source*
3
3
3
3
Action Level
250.0 mg/kg
250.0 mg/kg
250.0 mg/kg
150.0 mg/kg
Type of
Limit"
Step
Reference
CAC/RS 78-1974
CAC/RS 81-1976
CAC/RS 99-1978
CAC/RS 101-1978
Toxaphene
Zinc
Animal feed, processed 1 0.5 ppm
Vegetables 1 1.0 ppm
Fruits 1 1.0 ppm
Non-pulpy black currant nectar 3 5.0 mg/kg
CPG 7141.01-B.12
CPG 7141.01-B.12
CPG 7141.01-B.12
CAC/RS 101-1978
(Sheet 5 of 5)
From Lee et al (1991)
-------
Table B6
Action Levels and Maximum Concentrations for Contaminants in Aquatic
Organisms tor
centrati
Human
Consumption
Chemical
Aldrin
Antimony
Arsenic
Cadmium
Chlordane
Copper
Food
Rsh and shellfish
All nonspecified foods
(including seafood)
Fish, Crustacea,
molluscs
Fish
Molluscs
Fish
Molluscs
Action Level*
mg/kg (wet
weight edible
oortions)
0.3
0.3
Maximum
Concentration**
mg/kg (wet
Weight edible
Portions)
1.5
1.0
0.2
1.0
70.0
^ /"\ f\
DDT, DDE, TDE
Dieldrin
Endrin
Heptachlor, heptachlor
epoxide
Hexachlorocyclohexane
(Benzene
hexachloride)
Kepone (Chlordecone)
All nonspecified foods
(including seafood)
Fish
Fish and shellfish
Fish and shellfish
Fish and shellfish
Frog legs
Fish and shellfish
Crabmeat
5.0
0.3
0.3
0.3
0.3
0.4
10.0
0.5
(Continued)
US Food and Drug Administration (FDA) action levels for poisonous or deleterious
substances in human food, CPG 7141.01,1987.
Australian National Health and Medical Research Council Standards for metals in
food. May 1980.
Action level is for these chemicals individually or in combinations. However, in
adding concentrationa, do not count any concentrations below the folloqing levels:
Chemical
DDT, DDE, TDE
Heptachlor, heptachlor epoxide
Minimum Level, ma/kg
0.2
0.3
B-11
-------
Table B6 (Concluded)
Chemical
Lead
Mercury
Methyl mercury
Mirex
PCB (total)
Selenium
Tin
Toxaphene
Zinc
Food
Molluscs
All nonspecified foods
(including seafood)
Fish, Crustacea,
molluscs
Fish, shellfish,
other aquatic
animals
Fish
Fish and shellfish
All nonspecified foods
(including seafood)
Rsh
Fish
Oysters
AN nonspecified foods
(includingseafood)
Action Level
mg/kg (wet
weight edible
portions)
1.0
0.1
2.0
5.0
Maximum
Concentration
mg/kg (wet
Weight edible
Portions)
2.5
1.5
0.5
1.0
50.0
1,000.0
150.0
* This is not an action level but is a tolerance limit established thorugh the rulemaking
process.
From Lee et al (1991)
MISCK3UIDANCE AP8
B-12
-------
REFERENCES
Chaney, R.L. et al, 1978. Plant Accumulation of Heavy Metals and Phytotoxicity Resulting from
Utilization of Sewage Sludge and Sludge Composts on Cropland, Proceedings of the National
Conference on Composting Municipal Residues and Sludges, Information Transfer, Inc., Rockville,
MD.
Chaney, R.L, 1983. Potential Effects of Waste Constituents on the Food Chain in Land Treatment
of Hazardous Wastes, Noyes Data Corporation, Park Ridge, N.J.
Davis, R.D. and Beckett, P.H.T., 1978. Upper Critical Levels of Toxic Elements in Plants, II:
Critical Levels of Copper in Young Barley, Wheat, Rape, Lenuce, and Ryegrass and of Nickel and
Zinc in Young Barley and Ryegrass, New Phytology, Vol. 80.
Davis, R.D. et al, 1983. Critical Levels of Twenty Potentially Toxic Elements in Young Spring
Barley, Plant Soil, Vol. 49.
Lee, C.R. et al, 1991. General Decision Making Framework for Management of Dredged Material:
Example Application to Commerce Bay, Wisconsin, Misc. Paper D-91-1, U.S. Army Engineer
Waterways Experiment STation, Vicksburg, MS.
Van Driel, W. et al, 1983. Comparison of the Heavy-Metal Uptake of Cyperus Esculentus of
Agronomic Plants Grown on Contaminated Sediments, Misc. Paper D-83-1, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, MS.
MISC\GU1DANCE.APB
B-13
-------
APPENDIX C
GEOSYNTHETICS IN WASTE CONTAINMENT SYSTEMS
In Section 1, six pathways that would potentially allow contaminants to escape a CDF were defined.
These pathways included (1,2) loss of soluble contaminants in the dredge slurry via effluent
discharge or leachate; (3) loss of contaminated dredge solids carried by surface water run-off; (4,5)
loss of contaminants by plant or animal uptake; and (6) loss from volatilization of contaminants into
the atmosphere. Geosynthetic components are key to the design and performance of traditional
hazardous and solid waste containment systems. This appendix reviews applications of
geosynthetic components in waste containment systems. Section 6 examines the use of these
components for limiting contaminant pathways in the CDF contaminant basin. Section 7 presents
the use of geosynthetic components in the final closure of a CDF.
Contaminant pathways in conventional waste containment systems are controlled using a system of
barrier layers to limit the movement of liquids (leachates), drainage/collection layers that remove the
liquids to minimize the hydraulic head acting on the barrier layer, and filter layers that prevent
clogging of the drainage system and maintain separation of the layers. For hazardous wastes, EPA
minimum technology guidance (MTG) is based on the waste containment system shown on Figure
C.1. This system uses two lining systems, an upper geomembrane and a lower composite liner
consisting of a geomembrane over a clay liner. Above each of the two liners is a leachate
drainage/collection system that removes trapped leachate and prevents the development of a large
hydraulic head on the liner. A minimum of one filter layer is required to ensure operation of the
upper drainage system.
C.1 Barrier Systems
Barrier layers are designed to limit the movement of water and contaminants across the layer. Such
barriers include compacted clay layers, asphalt layers, and geosynthetic layers. These layers limit
the movement of contaminants by advective transport across the layer but do not completely limit
diffusion of contaminants across the layer. For contaminants associated with CDFs and typical
waste containment applications this limitation is acceptable.
Common synthetic barrier systems include geomembranes and geosynthetic clay liners (GCLs).
Both barriers systems are commercially manufactured, delivered to the field in large rolls or panels,
and are commonly used both alone and in conjunction with a conventional soil liner/barrier system.
The geomembranes have been the subject of extensive EPA research. Technical guidance
documents (TGDs) are available to aid in geomembrane selection, design, and installation. GCLs
are relative new-comers to waste containment applications but have been evaluated in limited EPA
workshops and are the subject of current EPA research. At present, EPA recommendations limiting
the use of GCLs to covers and as a component in the primary liner of a RCRA C waste containment
cell.
C-1
-------
5.1.1 Geomembrane Barrier Systems
Proper application of a geomembrane to waste containment systems requires evaluation of the
following: chemical compatibility of the geomembrane with the contaminants; proper design of the
geomembrane to protect and limit stresses in the membrane; and construction quality assurance to
ensure proper installation. Guidelines for all evaluations can be based on available technologies
developed initially for hazardous waste containment:
Chemical Compatibility of Geomembrane The chemical compatibility of a geomembrane with
a waste teachate must be evaluated using the EPA Method 9090 test. This test requires a long test
period, exceeding 120 days, and a quantity of the anticipated leachate. Most geomembranes will
absorb constituents of the leachate and swell during exposure to leachates containing organics.
Exceptions include PVCs that may loose plasticizer due to the organics and shrink. The chemical
resistance of a geomembrane is related to the solubility of the polymer in the leachate, crosslinking
of the polymer, degree of crystallinity, nature of the filler in the compound, and the molecular weight
(MW) and MW distribution of the polymer. It is therefore difficult to generalize regarding chemical
compatibility.
Design of Geomembrane Liner Comprehensive design guidelines for geomembranes are
available in the literature ( Richardson and Koerner, 1988 and Koerner, 1991) and are beyond the
scope of this documents. General geomembrane design objectives and key design considerations
are, however, reviewed in this section. The design of a geomembrane must ensure that the
membrane experiences minimal tensile stresses in service and is not damaged by puncture during
installation or service. Key design considerations include the following:
Puncture A geomembrane must be protected from puncture during installation and as waste is
placed in the facility. During placement, the geomembrane can be damaged by
foreign objects such as sticks or large gravel particles or rocks within the adjacent
soil. It is possible to protect the geomembrane from damage by using a cushion layer
of sand or geotextile. Generally the soil adjacent to the geotextile must have a
maximum particle size less than 1 inch. Placement of sediments directly on a
geomembrane would be impacted by the dredging method used, e.g. slurry versus
clamshell.
Stability Common geomembranes, particularly HOPE, have a very slick surface that can
create stability problems when used on slopes. The stability of dikes constructed
with internal geomembrane barriers would have to be evaluated. Laboratory testing
to determine interface friction angles is normally required on a site by site basis.
Anchorage Geomembranes must be anchored at their perimeters to prevent wind from blowing
under the membrane. Such anchorage may be of temporary value if the membrane
is to be buried within the system eventually. The anchorage system must be
C-2
-------
designed so that the strength of the anchorage is less than the strength of the
geomembrane. Thus failure of the anchorage should result in pullout and not tearing
of the membrane.
Weirs Liquids contained by the geomembrane must be removed from the CDF through a
weir or a sump. The connection of the geomembrane to a structural weir system
requires the use of battens and consideration of potential differential settlements.
Additional design considerations unique to CDFs include evaluating the impact of the geomembrane
of the consolidation of the sediments, placement of geomembranes having a specific gravity less
than 1.0 in marine environments, and the potential for a partial barrier in the dike only. Specific
design considerations for geomembranes are provided in the pathway evaluations provided in
Sections 6 and 7.
In recent years, a commercial system of interlocking HOPE panels has been used to construct very
low permeability vertical barriers (EPA, 1992a). These walls can be constructed within excavated
trenches or in slurry trenches depending upon site conditions. Each HOPE panel interlocks with
adjacent panels, see Figure C-3, similar to those used in conventional sheet pile walls. The vertical
barriers can be used to restrict the outward migration of liquids or to restrict the inward migration of
ground water.
Construction Quality Assurance (CQA) EPA has prepared specific recommendations for CQA
programs developed to ensure that the geomembrane is properly installed (EPA/530/SW-91/051).
CQA programs are a planned series of activities performed by the owner o ensure that the facility is
constructed as specified in the design. There are five elements to a CQA program: (1) responsibility
and authority, (2) CQA personnel qualifications, (3) inspection activities, (4) sampling strategies, and
(5) documentation. Much of the CQA program for geomembranes focuses on the quality of field
seams and detection construction damage. The end product of the CQA program is a certification
document prepared by the CQA team to demonstrate that the geomembrane was installed as
specified in the design. As-built drawings indicating field modifications, seam failures, patches, etc.
are also part of the certification document.
C.1.2 GCL Barrier Systems
GCLs are made by sandwiching bentonite granules between two geotextiles to form rolls or large
panels of liner. The sandwich is held together using either a water soluble adhesive or by needling
the two geotextiles together. Typical GCLs provide approximately one pound of bentonite per
square foot and have a dry thickness of approximately 1/4 inch. GCL barrier layers have been used
in CERCLA containment systems and covers over uranium mine tailings (e.g. UMTRA program)
since 1988. They have the advantages of being easily placed in the field, inexpensive (especially if
local clays are not available), and very tolerant of field abuse. During the past two years, the use of
C-3
-------
GCLs in waste containment systems has been the subject of two EPA technical workshops.
Ongoing research related to these workshops has focused on the following concerns:
Stability As the bentonite in the GCL hydrates (absorbs water), the shear strength of the CGL
can decrease significantly and create a plane of weakness within the facility;
Seams GCL panels are joined by simply overlapping adjacent panels such that the integrity
of the seam is dependent on the swelling and partial extrusion of the bentonite; and
Chemical The permeability of the bentonite used in the GCLs can be significantly increased by
the presence of leachate having a high ion exchange capacity.
GCLs may offer significant advantage for facilities such as CDFs where access for traditional
construction equipment associated with clay liners is limited.
C.2 Drain/Collection Systems
Waste containment systems that include barrier layers must also include adjacent layers that collect
and remove the liquids retained by the barriers. Such drainage/collection drains traditionally have
been constructed using sand or gravel layers. This same function can be performed by geonet
drainage elements. Geonets are formed with a minimum of two layers of ribs oriented to produce a
high planar flow capacity. The geonets are formed in a counter-rotating extruder and are typically
1/4 inch thick from the top of the upper rib to the bottom of the lower rib. Geonets can provide the
same planar flow capacity as a 12 inch layer of sand having a permeability of 10'2 cm/sec due to the
high flow velocities within the net. The hydraulic flow capacity of a geonet is typica'ly expressed as
transmissivity (the product of layer thickness times layer permeability) as a function of gradient and
normal pressure as shown on Figure C.2. The transmissivity of a geonet will decrease with
increasing hydraulic gradient and normal stress.
There are two main concerns with geonets: first the crush strength at the intersection of the ribs
must be sufficient to resist buckling and creep deformations during the service life of the geonet; and
secondly adjacent layers must be prevented from intruding into the net voids when stressed by
service loads. The latter problem is particularly important if the geonet is placed immediately
adjacent to soft soils, such as dredge sediments, that can plastically flow between the ribs.
Geogrids are commonly available with a geotextile filter fabric bonded to one or two faces. Such
products are called geocomposites and provide both drainage and filter systems in the same
product. Geosynthetic filter systems are discussed in Section C.3.
One significant short coming of geonets compared to conventional sand drains is the reduced
hydraulic storage capacity of the nets. Sand and gravel drainage layers can store a significant
volume of water within their pore spaces. Geonets, however, are only a 1/4 inch thick and therefore
C-4
-------
have almost no storage capacity. The use of geonet drains requires a liquid removal system that
functions continually, but at possibly a very slow rate of removal.
C.3 Filter Systems
Conventional filter systems are designed using graded layers of sands and gravel that increase the
average particle size in the direction of flow. The filter criteria for natural soils follow basic criteria
established by Terzaghi in 1922. The four main requirements of natural filters are:
1 - The filter material should be more pervious that the base material to ensure that no
hydraulic pressure will build up to disrupt the filter and adjacent structures.
2 - The voids of the in-place filter material must be small enough to prevent base
material particles from penetrating the filter and clogging the filter system.
3 - The layer of the protective filter must be sufficiently thick to provide a good
distribution of all particle sizes throughout the filter.
4 - Filter particles must be prevented from movement into adjacent coarser layers or
pipes.
Geotextile filter design parallels sand filter design with some modifications. Three of the above
design elements remain the same: adequate flow, soil retention, and clogging.
Adequate flow thmuah a geotextile is assessed by comparing the allowable permittivity (
permeability divided by thickness ) with that required to prevent build up of pressures within the
base layer. Permittivity of a geotextile is obtained using the ASTM D4491 test method. Typical
geotextile filters have sufficient permittivities when used adjacent to sands and fine grained soils.
Soil retention for a geotextile is requires determining the effective opening size of the geotextile, O95.
The O95 of a geotextile is the opening size at which 5% of a given size glass bead will pass through
the fabric. It is well established that the O95 of a geotextile is related to the particle size to be
retained by the following type of relationship:
095
-------
Institute (GRI), test method GT1. Both tests place a sample of the actual soil to be retained against
the geotextile and then flow water through the system. The test apparatus common to both the COE
and GRI tests is shown on Figure C.3. The Gradient Ratio Test measures the increase in hydraulic
gradient across the geotextile with an increase in gradient indicating increasing clogging. The GRI
test simply monitors the flow rate out of the system under a constant system gradient. The flow rate
should decrease slightly but then achieve an equilibrium flow rate. An ever decreasing flow rate
indicates a clogging problem. The Gradient Ratio test can be performed in several days while the
GRI test can require several months time.
Additional long term clogging of a geotextile may be cause by biological growth activity or from
solids that precipitate from the water. Leachates rich in biological matter or potential percipitants
should be tested using the GRI test.
REFERENCES
EPA, 1989. Technical Guidance Document: Final Covers on Hazardous Waste Landfills and
Surface Impoundments, EPA/530-SW-89-047.
EPA, 1991. Technical Guidance Document: Inspection Techniques for the Fabrication of
Geomembrane Field Seams, EPA/530/SW-91/051.
EPA, 1991. Technical Resource Document: Design, Construction, and Operation of Hazardous
and Non-Hazardous Waste Surface Impoundments, EPA/530/SW-91/054.
EPA, 1992. Technical Guidance Document: Construction Quality Management for Remedial Action
and Remedial Design Waste Containment Systems, EPA/540/R-92/073.
EPA, 1991. Seminar Publication: Design and Construction of RCRA/CERCLA Final Covers,
EPA/625/4-89/022.
EPA, 1987. Technical Guidance Document: Geosynthetic Design Guidance for Hazardous Waste
Landfill Cells and Surface Impoundments, EPA/600/S2-87/097.
EPA, 1992a. Draft Technical Guidance Document: Quality Assurance and Quality Control for
Waste Containment Facilities, Hazardous Waste Engineering Research Laboratory, Cincinnati, OH.
C-6
-------
Filter Layer
Primary FML
Secoaary FMl \.
c
"S
£
a
«
tr
I
Native Soil Foundation
(Not to Scale)
Figure C-l RCRA Minimum Technology Guidance Landfill
= 1
= 05
= 025
= 0.125
= 00625
= 0.03125
i = gradient
0 5.000 10,000 15.000 20,000
Normal Stress (Ibs/sq. ft)
FML - Geonet FML Composite
Figure C-2 Hydraulic Flow Capacity of Geonets
C-7
-------
Figure C-3 Geomembrane Vertical Cutoff Wall Joints
-,
HAKE FLOW KATE
REAOUCS FROn
THIS OUTFLOW
INFLOW
CHO
WATER OUTFLOW
' PORT
1ANOMETERS
-CEQTEX-1LE
1
I 3
i
1
1
°ERMEA1ETER
CONSTANT HEAD DEVICES
Figure C-4 Gradient Ratio Test Device
C-8
-------
APPENDIX D
CDF - REGION 5 SUMMARY TABLES
-------
Table D-1
Technical Specifications for In-Lake CDFs
Facility
Cleveland
Dike #12
(1974-1979)
Cleveland
Dike #14
(1979- )
Lackawanna
Dike #4
(1974- )
Erie
(1979- )
Huron
(island)
(1975- )
Loram
(1977- )
Buffalo
(1968-1972)
Times
Beach
(1972- )
Capacity
(MCY)/
% Filled
2.8/100
6.1/40
6.9/40
1.640
2.1/70
1.9/70
1.5/100
1.5/45
Acres
Area
56
88
100
22
63
58
33
45
Dike
Construction
Rubble mound
Rubble mound
with sheetpile
cutoff
Rubble mound
Rubble mound.
& sheetpile
each face
Rubble mound
& cellular
sheetpile &
filter cloth
Rubble mound
& sheetpile
Soil & slag
core&
limestone
riprap
Layered slag
& rubble
mound
Liner/
Cap Design
None/None
None/None
None/None
None/None
None/None
None/None
None/6 feet &
construction
ddbris
None/None
Dewaterin
g
System
None
2 overflow
weirs
Thru dike
and
overflow
weir
Overflow
weir - dike
filter
Thru dike/
pumping/
weirs
Weir
Thru dike
Thru dike
Effluent
Treatmen
t
Natural
settling
Natural &
granular
dike filter
-2 oil
skimmers
Dike filter
- natural
settling
Dike filter
& natural
settling
1-hour
settling
before
pumping
to lake
Dike filter
& setting
Natural
setting
Dike filter/
natural
settling
MCY = million cubic yards
mCY = thousand cubic yards
D-2
-------
Table D-l (Continued)
Facility
Toledo/
Facility #4
(1976- )
Toledo/
Grassy
Island
(1967-?)
CHICAGO
DISTRICT
Chicago/
Calumet
Harbor
(1984- )
DETROIT
DISTRICT
Bayport/
Green Bay
H 965-1 979)
Bolles
Harbor
(1978- )
Clinton River
(1978- ?)
Erie
Pier/Duluth
(1979- )
Capacity
(MCY)/
% Filled
10/65
5.0/100
1.3/20
5.5/100
0.33/25
0.37/98
1.1/65
Acres
Area
242
150
42
400
25
30
82
Dike
Construction
Limestone
base with clay
dike
Granular fill
(sandy loam)
Stone filled
with limestone
core
On-site
material
Limestone
with clay core,
sheetpile
revetments &
filter cloth
Dredged
material from
Clinton River
channel,
includes rip-
rap
On-site and
dredged
material with
stone np-rap-
300' steel
bulkhead on
S.E. side
Liner/
Cap Design
Clay core/None
None/None
Plastic liner (30
mil)/2-foot clay
liner & topsoil at
closure
None/cap
planned
None/None
On-site clay/clay
20 mil PVC
liner/None
Dewaterin
g
System
Overflow
weir
Overflow
weir
Pump thru
filter cells
Overflow
weir
Overflow
weir
None
None
Effluent
Treatmen
t
Natural
settling
with oil
skimmer
Natural
settling
Primary
and
secondar
y
settling/sa
nd-carbon
filtration
Natural
settling
Natural
settling &
oil
skimmer
Natural
settling &
oil
skimmer
None-no
outlet for
effluent
D-3
-------
Table D-i (Continued)
Facility
Grassy
Island/
Wyandotte
(1960-1984)
Kenosha
(1975- )
Kewaunee
(1982- )
Kidney
Island/Green
Bay
(1979-1986)
Manitowoc
Harbor
(1975- )
Milwaukee
(1975- )
Monroe/
Sterling Park
(1986- )
Pointe
Mouillee
(1979- )
Capacity
(MCY)/
% Filled
1.9/100
0.75/66
0.50/57
1.2/97
0.80/61
1 .6/44
4.2/0
18.6/38
Acres
Area
80
32
28
60
24
61
89
700
Dike
Construction
Sand and clay
dikes
Rubble mound
with sheetpile
cutoff &
graded filter
core
Limestone
core/rip-rap
and filter
discharge cell
Rubble mound
with sheetpile
cutoff and
filterstone core
Rubble mound
with sheetpile
cutoff &
filterstone core
with geofabric
Limestone
core & cover
with sand filter
on granular
fill/sheetpile on
south side
Limestone
core with
grouted
mattress on fill
and rip-rap at
lake
Limestone &
clay core with
coverstone,
consists of 5
cells
Liner/
Cap Design
None/None
None/None
None/None
None/None
None/None
None/None
2' bentonite &
granular fill/
None
None/None
Dewaterin
g
System
Overflow
weir
Thru dike
& filter cell
Thru dike
core & 4
filter cells
Thru core
& filter cell
Thru core
& filter cell
Thru dike
core &
filter cell
Overflow
weir &
filter cell
Overflow
weir
II
Effluent
Treatmen
t
Natural
settling
Natural
settling &
flow-thru
dike&
filter cell
Natural
settling &
flow-thru
filters I
Natural
settling &
filter cell
Natural
setting &
filter cell
Natural
settling
Natural
settling &
filtration
Natural
settling
I
D-4
-------
Table D-l (Continued)
Facility
Riverview
(1978- )
Saginaw
(1978- )
Renard I.
(1979- )
Capacity
(MCY)/
% Filled
0.12/84
10/48
1.2/97
Acres
Area
11
283
60
Dike
Construction
Clay dike with
bentonite
slurry wall in
lake sands &
clay
Limestone
dike with
coverstone
Liner/
Cap Design
None/None
None/PCB
sediments
capped with less
polluted
sediments
Dewaterin
g
System
overflow
weir, in
1982
underdram
added
Overflow
weir
Effluent
Treatmen
t
Natural
settling,
oil
skimmer
Natural
settling,
oil
skimmer
Avg.
3.5 MCY 112 ACRES
D-5
-------
Table D-2
Technical Specifications for Upland CDFs
Facility
Capacity
(MCY)/
% Filled
BUFFALO DISTRICT
CHICAGO
DISTRICT
Michigan
City
(1978-1987
DETROIT
DISTRICT
Dickinson
Island
(1976- )
Frankfort
Harbor
(? - ?)
Harbor
Island
(1974-?)
Harsen's
Island
(1975-1980)
Crooked
River
(1982- )
Kawkawlin
River
(1989-90)
Monroe
(Edison)
(1979-1984)
0.05/100
2.0/48
0.07/100
0.31/97
0.10/100
0.02/32
NA/100
NA/100
Area
Acres
Dike
Construction
None
3.3
174
80
36
17.2
9
NA
43
Earth dike with
stone rip-rap
Clay dikes
No dikes
required
Clay berm
Clay dike
Local soil dike
Clay and sand
berm
Preexisting/
earth berm
with clay layer
inside
Liner/Cap
Design
Natural clay
under CDF/clay
cap with topsoil
None/None
None/Site to be
seeded
None/None
None/To be
leveled &
revegetated by
State of
Michigan
None/None
None/None
None/None
Dewaterin
9
System
Effluent
Treatment
Sand filter
&
drainpipes
Overflow
weir & oil
skimmer
None
Overflow
Weir
Overflow
weir
None
Overflow
weir
Overflow
weir
Primary
settling &
sand
filtration
Natural
settling
None
Natural
settling &
oil skimmer
Natural
settling
None
Natural
settling
Natural
settling
D-6
-------
Table D-2 (Continued)
Facility
Port Sanilac
Village
(1979-1983)
Keweenaw
Waterway
(7 - ?)
Sebewaing
(1979- )
Verplank/
Grand
Haven
(1974-1977)
Whirlpool
(1978- ?)
Windmill
Island
(1978-1988)
Capacity
(MCY)/
% Filled
0.14/100
0.24/23
0.08/54
0.13/100
0.03/100
0.16/100
Area
Acres
13
21
9
19
14
16
Dike
Construction
On-site soil
berm with clay
cover
Clay Dikes
Rip-rap over
filter cloth on
clay core,
sheetpile
cutoff
Clay berm
Clay dike
clay dike
Liner/Cap
Design
None/None
None/None
None/None
Plastic
membrane/
None
None/None
Dewaterin
g
System
None
Overflow
Weir
Overflow
weir
Overflow
weir
Overflow
weir
Effluent
Treatment
None
Natural
Settling
Natural
settling, oil
skimmer
Natural
settling
None
Avg.
0.28 MCY 36 ACRES
D-7
-------
Table D-3
Summary of Contaminated Sediment Remedial Actions
in Great Lakes Region
Facility
Contamination/
Action Date
Site
Sediment
Volume
(mCY)
Remedial Action
A) CERCLA Remediations (1980)'
1) Cast Forge
Steel Co.,
Howell, Ml
2) Crab Orchard
National
Wildlife Refuge,
Carterville, IL
3) Dayton Tire and
Rubber Co.,
Dayton, OH
4) Fields Brook,
Ashtabula, OH
5) Moss American
Co., Milwaukee
County, Wl
6) P. R. Mallory,
Crawfordville,
IN
7} Tecumseh
Products Co.,
L. Sheboggan
River, Wl
PCB to 4800 ppm,
1977
Cadmium to 780
ppm, chromium to
889 ppm, lead to
20,500 ppm, PCB
to 88,000 ppm,
plus other metals-
-NPL 1984
1600 gallons of
PCB-
contaminated oil
released- 1987;
sediment PCB to
6020 ppm
NPL 1983; variety
of organics and
heavy metals
CPAH (creosote)
to 500 ppm and
PAH to 5900 ppm-
-NPL1980
PCBs to 165,402
ppm in soil and
9695 ppm in
ravine sediments-
1985
PCB to 4500 ppm
plus chromium,
cadmium, lead,
mercury, zinc,
nickel-NPL1985
South Branch
Shiawassee
River, 8 miles long
Several scattered
industrial sites
Wolf Creek
Fields Brook and
2-mile reach of
Ashtabula River
5-mile stretch of
Little Menomonee
River
Ravine that leads
to Little Sugar
Creek
14 miles of L.
Sheboygan River
upstream of
mouth and
Sheboygan harbor
Initial 2.3 by
1982
About 6.4 total
About 0.2 total
16mCY
sediments
with organic
contaminants
and 25 mCY
immobile
contaminants
5.2 mCY
along river
corridor
60 mCY by
June 1990-
more
excavation
planned
2.7 mCY plus
Initial dredge and landfill
incomplete-put on NPL
(1983; action pending)
Excavation and
treatment or landfilling
(action pending)
August 1 987-
excavation and
landfilling-further
remediation needed
Excavation, dewatering,
incineration,
solidification, placement
in RCRA/TSCA landfill
and fluids treated
Co.istruct new river
channel-excavate, treat
with slurry bioreactor,
dispose in on-site
landfill
Remediated to 25 ppm
PCB level-placed in
hazardous waste landfill
Excavation, containment
and treatment plus in-
situ containment-ROD
in 1993
mCY = thousand cubic yards
MCY = million cubic yards
D-8
-------
Table D-3 (Continued)
Facility
8) Outboard
Marine Corp.,
Waukegan, IL
9) Westinghouse
Electric Co.,
Btoommgton, IN
Contamination/
Action Date
PCB to 25,000+
ppm-over 1
million pounds
disposed- 1976
PCB discharged
to sewage
treatment facility-
August 1985
Site
Waukegan Harbor
and on OMC
property
PCB in local
landfill sludge and
streams
Sediment
Volume
(mCY)
8 mCY with
greater than
500 ppm PCB
and 30 mCY
with 50 to 500
ppm
650 mCY of
contaminated
materials
Remedial Action
Isolation of Slip 3
hotspot by slurry wall,
excavation of upper
harbor and parking lot
with 750 ppm, treatment
and placement as cover
on slip 3
Landfills capped by
1987, creek sediments
were dewatered,
excavated and stored
with incineration
pending
B) CLEAN WATER ACT (1977) amended 1987, 1990
1) U.S. Steel Gary
Works, Gary, IN
2) U.S. Steel,
Loram, OH
PAHs, heavy
metals, oil and
grease-October
1988
Coke (PAH) from
steel plant-PAH
over 50 ppm,
cadmium over 30
ppm-January
1979
5- to 12-mile
section of Grand
Calumet River
Black River
500 mCY over
5-mile stretch
of river
SOmCY
Recycling of sediment
pollutants back into
steel-making process
Dredging and placement
in on-site landfill
C) RCRA/TSCA REMEDIATIONS None
D) STA TE A CTIONS FOR REMEDIA TION
1) ALCOA,
Lafayette, IN
2) Dana Corp.,
Churubusco, IN
3) Deer Lake, Ml
Sediment PCB
greater than 50
ppm- 1982
PCb in sewage
treatment sludge
and drainage ditch
sediments to 7290
ppm-Spring 1986
Mercury to 15
ppm (v. high) in
Deer Creek
sediments and
fish-1982
One mile reach of
Elliot Ditch/Wea
Creek which flow
into Wabash River
Ditches feed into
Eel River
Deer Lake is
connected to Lake
Superior by Carp
River
5.6 mCY
Upper 12- 18
inches of
sediment
excavated
with backhoe
?
Damming of stream,
treatment of water to
.0005 mg/l. Sediment
solidified with lime and
flue dust-placed in
landfill
Water treated to 0.1
ppb, sediments
stabilized with kiln dust
and placed in PCB
landfill
Lake level stabilized to
allow clean sediment
covering of
contaminated sediment
over 1 0-year period
D-9
-------
Table D-3 (Continued)
Facility
4) Double Eagle
Steel,
Dearborn, Ml
5) Hitachi
Magnetics
Corp., Edmore,
Ml
6) Dayton Power
and Light,
Dayton, OH
7) Lake Lansing,
Ml
8) Little Lake
Butte, Des
Morts, Wl
9) Starkweather
Creek,
Madison, Wl
10) PPG Industries,
Inc , Circleville,
OH
Contamination/
Action Date
Zinc from plating
operation entered
river for 5 months-
-October 1986
PCB and mercury
plus cadmium,
chromium,
copper, nickel,
lead, zinc, oil and
grease
PCB greater than
50 ppm-
November 1985
Dredging of
sediments with
arsenic
Demonstration
project by WDNR-
-PCB hotspot
contains about
1650 kg of PCBs
WDNR
demonstration
project for Creek
Sediment
Restoration-
mercury, zinc,
lead, oil and
grease
PCBs leaked into
sewer drains
discharging into
Scioto Creek-
PCBs up to
710,000 ppm-
Spnng 1988
Site
Rouge River for
200 yards
About one mile of
Wolf Creek
Oppossum Creek
Lake Lansing is
about 450 acres
Paper mill PCBs
along Little Lake
Butte, Des Morts
and 7-mile stretch
of Lower Fox
/River
Starkweather
Creek enters into
Lake Monona
causing decay of
lake
Scioto Creek
Sediment
Volume
(mCY)
39mCY
7
1.6mCY
1 .6 mCY to
restore lake-
demonstration
project
56mCY
?
Sediments still
being
removed- 1-2
mCY
anticipated
Remedial Action
Sediment dredged and
placed in USAGE Point
Mouillee CDF
Excavation and
placement in licensed
landfill or TSCA landfill
Soils and sediments
were excavated to less
than 25 ppm of PCBs
and placed in a PCB
landfill in Ohio
Dredged sediments
placed in three upland
CDFs and effluent
monitored
Dredging or in-place
isolation of hot spot is
planned.
Dredging of creek by
backhoe and placement
in a diked CDF
Dewatering, stabilization
of sediments,
excavation and
placement in landfill
D-10
-------
APPENDIX E
RCRA-C HAZARDOUS WASTE LANDFILL
PERFORMANCE CRITERIA
A.1 Introduction
Current EPA minimum technology requirements for new hazardous waste landfills, surface
impoundments, and waste piles require (40 CFR 264.221)
... two or more liners and a leachate collection system between liners. The liners and leachate
collection system must protect human health and the environment... The requirement for the
installation of two or more liners... may be satisfied by the installation of a top liner designed,
operated and constructed of materials to prevent the migration of any constituent into such
liner during the period such facility remains in operation (including any post-closure monitoring
period), and a lower liner designed, operated, and constructed to prevent migration of any
constituent through such liner during such period.
The specific minimum properties of this multiple liner system are defined as follows (40 CFR
264.301):
A top liner designed and constructed of materials (e.g., a geomembrane) to
prevent migration of hazardous constituents...
A composite bottom liner, consisting of at least two components. The upper
component must be designed and constructed of materials (e.g., a
geomembrane) to prevent... The lower component must be constructed of at
least 3 feet (91cm) of compacted soil material with a hydraulic conductivity of
no more than 1x10"7 cm/sec.
The maximum head of leachate acting on a liner is 30 cm.
Figure A.1 shows the layers associated with the prescriptive RCRA-C liner system.
A.2 Oe Minimus Leakage
The RCRA-C liner system is designed with the goal to allow no more than the "de minimis"
leakage of contaminants. The concept of "de minimus" comes from the legal principal "de
minimis non curat lex" (i.e., the law does not concern itself with trifles). Specific levels of
acceptable leakage have not been codified but it is possible to estimate the minimum total
leakage from a "perfectly" constructed RCRA-C liner system. The downward vertical flow of
liquids through the RCRA-C system is slowed as follows:
The clay liner allows a maximum vertical downward flow velocity of 1x10"7
E-1
-------
cm/sec based on Darcy's law and a vertical gradient of one. This is
approximately 9.2 gallons/acre/day.
A geomembrane liner will allow liquids to diffuse through the liner based on
Pick's first law. The rate of diffusion is controlled by the the water vapor
transmission (WVT) rate of the polymer. WVT is expressed in units of g m"2 d"1
where the transmission of 1g m2 d"1 is equal to approximately 1.07 gal per acre
per day (EPA/600/2-88/052). WVT values for common geomembranes used in
such facilities range in value from 0.006 to approximately 2.0. Thus the
geomembrane liner will allow up to 2 gallons/acre/day leakage. Note that this
rate is not influenced by the head acting on the geomembrane.
EPA generally believes that the total leakage through composite liner systems (geomembrane
overlying a compacted clay liner) should be less than 1 gallon/acre/day based on the above
geomembrane flow rates.
A.3 Liner Equivalence - RCRA-C
The construction of the RCRA-C barrier system in an in-iake environment would be impossible
or at the least very expensive. However, an equivalent system can be constructed using clean
low permeability dredged material. Three factors are usually considered in evaluating the
equivalence of barrier systems:
the flow rate through the liner system (e.g.1 how many gallons per acre per day),
the "break-out time" defined as the time required for liquids to travel through the
system and be released to the environment, and
an equivalent chemical adsorption capacity.
The flow rate through the liner system will be controlled by the least permeable barrier in th<=>
system. The RCRA-C liner system is flow limited by the geomembranes used, with flow rates
up to 2 gallon/acre/day. This same flow rate can be achieved by a soil layer having a hydraulic
conductivity of less than approximately 3x1 O'8 cm/sec assuming 30 cm of head acts on the
surface. As previously shown on Figure 6.6, fine grained dredge sediment can achieve such
low levels of permeability after consolidation. The head acting within CDFs can be expected to
significantly exceed 30 cm. However, the thickness of fine grained dredge materials would
probably also exceed the 3 foot thickness of the RCRA-C soil liner. Therefore it may be
possible to construct a dredge liner approaching the flow rate criteria of a RCRA composite
liner.
The minimum break-out time of a liquid moving through the RCRA-C liner system can be
calculated by summing the travel times through the individual barriers under the influence of
the allowable 30 cm (1-ft) of leachate head as follows:
Primary and secondary geomembranes; 60-mil thickness and 1 gallon/acre/day
flow rate (k equivalent of 4.27x10'9 inch/sec)
travel time = 0.060 inch / 4.27x10'9 inch/sec = 162 days
E-2
-------
Secondary composite soil liner; 3-feet of 1x10'7 cm/sec soil
travel time = 3 feet / 1x107 cm/sec = 10580 days
The total minimum travel time can then be calculated to equal 162+162 + 10580 or 10904
days. This same travel time is possible with a soil liner having a maximum hydraulic
conductivity of 3x10"8 cm/sec and a thickness of 27 cm or approximately 1 foot in thickness.
The increased head acting within the CDF would obviously reduce the travel time. Note that it
is possible to design a liner system such that the break out time exceeds the life of many
contaminants.
Chemical adsorption capacity is dependent upon the cation exchange capacity (CEC) of the
liner clay and the chemical characteristics of the contaminant of concern. This equivalence
must be verified on a site by site basis.
Based on this evaluation, it appears very possible that a barrier system could be constructed
using a single layer of fine grained dredged material that would approach, but not fully achieve,
the performance standards of the RCRA-C liner system.
A.4 Commentary on Liner Equivalence - RCRA-D
RCRA-C regulations in 40 CFR 258 provide for an alternative method of evaluating liner
equivalence. In these regulations, a point of compliance method allows the use of alternative
liner system if it can be shown that the liner will limit contaminant migration such that
contamination concentrations at the closest down-gradient monitoring well is less than MCLs
specified by the CWA. Presently, EPA requires this evaluation to be performed using the EPA
generated computer model MULTIMED (Allison, 1992). This model uses a closed-form solution
to the contaminant transport problem and incorporates default chemical data.
Reference
EPA, 1 988. Lining of Waste Containment and Other Impound Facilities, EPA/600/2-88/052,
Risk reduction Engineering Laboiatory, Cincinnati, Oh, 45268.
Allison, T.L., 1992. Using MULTIMED To Evaluate Subtitle D Landfill Designs, Contracr 68-
WO-0025, Office of Solid Waste, Washington, D.C.
Koerner, R.M. and D.E. Daniel, 1993. "Technical Equivalency Assessment of GCLs to CCLs,"
Geosynthetic Liner Systems: /novations, Concerns and Design, R.M. Koerner and R.F. Wilson-
Fahmy (Eds), Industrial Fabrics Association International, St. Paul, Minn.
E-3
-------
MATERIALS
RECOMMENDED
DIMENSIONS AND SPECIFICATIONS
Graded Granular Filter Medum
Granular Drain Material
(bedding)
Flexible Membrane Liner (FML)
Granular Drain Material
(bedding)
Flexible Membrane Liner (FML)
Low Permeability Soil, Compacted in Lifts
(sal liner material)
NOTE.
Values for FML thickness represent
actual values at all points across
roll width FML thickness > 45 mils
recommended if liner is not covered
within 3 months
Thickness 2 6m.
Maximum Head on Top of Uner « 12 m.
Thickness >12m
Hydraulic Conducovny 21 x 1CT2 cm/sec
o
Drain Pipe-
Q
Thickness ol FML > 30 mils
(see note)
Thickness 2 12 in.
Hydraulc Conductivity 2 1 x 1 0-2cnvsec
* - Drain Pipe - +
Thickness of FML> 30 mis
(see note)
Thickness > 36 in.
Hydraulic Conductivity <1 x 10"7 cm/sac
Prepared in 6 in. Lifts
Surface Scarified Between Lifts
Unsaturateu _one
Groundwaler Level
NOMENCLATURE
Solid Waste
Filler Medium
Primary Leachale Collection
and Removal System
Top Uner (FML)
Secondary Leachate Detection
and Removal Sysbm
Compression Connection (contact)
Between Soi and FML
Bottom Liner (composite FML and
compacted low permaabiHy «ol)
Native Soil Foundation/Subcase
(EPA/600/2-88/052)
Figure A-1 Schematic Profile of Double Composite Liner System
E-4
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