Transcript What is Bioavailability? - CLU-IN

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Welcome – Thanks for joining
this ITRC Training Class
ITRC Internet-based training and
Technical and Regulatory Guidance
Incorporating Bioavailability Considerations
into the Evaluation of Contaminated
Sediment Sites (CS-1, 2011)
Sponsored by: Interstate Technology and Regulatory Council (www.itrcweb.org)
Hosted by: US EPA Clean Up Information Network (www.cluin.org)
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Meet the ITRC Trainers
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Diana Marquez
Delaware Department of
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[email protected]
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sclough@
haleyaldrich.com
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of Environmental
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greg.neumann@
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ITRC Sediments Team
States
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ITRC Web-based Guidance Outline
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Introduction and background on
bioavailability
Overview of bioavailability
processes
Bioavailability pathway exposure
assessment
• Screening
• Background
• Pathway exposure assessment
 Benthic invertebrates
 Fish and water column
invertebrates
 Wildlife
 Plants
 Human health

Risk management decision-making
http://www.itrcweb.org/
contseds-bioavailability/
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What You Will Learn…
The intended users of this guidance are
individuals who have a working
knowledge of contaminated sediment
management but seek additional
information about bioavailability.
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What is bioavailability?
When do we apply bioavailability
adjustments?
What are the available tools and how do we
use them?
How do we use the information to make risk
management decisions?
You will NOT learn how to conduct a Risk
Assessment that incorporates bioavailability.
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The Problem!

US EPA reports –
10% (1.2 billion yds3) of U.S.
sediment underlying surface water
pose a potential ecological or
human health risk

Cost of clean-up is in the trillions

Contaminant concentration in
sediment and actual exposure is
not a direct relationship

Bioavailability will give a more
accurate characterization of
exposure
Conventional Clamshell
Excavator
USACE 2008. Technical Guidelines
for Environmental Dredging of
Contaminated Sediments
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What is Bioavailability?
“…individual physical, chemical, and biological
interactions that determine the exposure of plants
and animals to chemicals associated with soils
and sediment (National Research Council, 2003).”
Specifically, bioavailability addresses the fact that
only a fraction of the contaminant concentration
present in the environment may be taken up or
result in an effect on an organism!
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How can Bioavailability Make a
Difference?

If contaminants are not physically accessible, or
chemically or biologically available, they should
not be included in the calculation of risk

Can optimize the extent of cleanup required to be
protective

Can provide optimization of remedial approach
and cost

Can be an important factor in balancing the risks
caused by remedial action
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How is Bioavailability Being Used?
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2008 – ITRC Team distributed questionnaire to
assess extent bioavailability was used for the
development of site cleanup levels
35 case studies collected
(Table 9-1 and Appendix D)
• Summarized exposure
pathways addressed
• Summarized contaminants
evaluated/addressed
• Summarized tools used at each site
• Includes contacts for more
information about each site
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Questionnaire Results
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Most common exposure pathways evaluated
• Benthic exposure
• Human health
• Pelagic exposure
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Most common tools used to assess bioavailability
• Bulk sediment chemistry
• Tissue sampling (fish,
bivalves, other water
column receptors)
• Porewater chemistry
• Bioassays of benthic
invertebrates
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Risk Management Role in DecisionMaking
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Risk management integrates the results of the risk
assessment with
• Technical
• Political
• Legal
• Social
• Economic objectives

Bioavailability is used to make
risk management decisions within the
• Risk assessment - Section 9.1
• Remedy selection – Section 9.2, Table 9-2
• Remedial design/Implementation – Section 9.2
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Risk Assessment
The assessment of risk to all receptors identified at a
contaminated sediment site related to
physical, chemical, and biological processes!
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Bioavailability should be used to actively refine conceptual site
model (CSM)
Risk assessment will likely involve a “weight of evidence” approach,
or “multiple line of evidence” approach
• Be aware of sources of variation in
risk assessments
• Collect data essential to risk assessment
• Analyze to understand exposure and risk
• Remember: bioavailability is highly site
specific
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Be aware of your stakeholder interests,
and communicate with them regularly
View ITRC’s Use of Risk Assessment in
Management of Contaminated Sites
(Risk-2, 2008) – available from
www.itrcweb.org
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Risk Assessment & Bioavailability

Advantages
• If contaminants aren’t bioavailable, then they aren’t included
in the evaluation of risk (no exposure)
• Optimization of cleanup goals, with a possible cost reduction
• More effective use of available resources
• Can achieve more accurate defensible cleanup goals while
ensuring protection of receptors

Challenges
• Uncertain acceptance by regulators, stakeholders, and the
public
• Bioavailability may vary across a site (or operational units)
• Potentially higher site characterization costs
• May take longer to gain full understanding of site conditions
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Remedy Selection

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Bioavailability evaluation within risk assessment process
will result in selection of remedy that will better address
concerns at site
Example: Mocks Pond Case Study
• Site history and bulk sediment testing identified
contaminants of potential concern (COPCs)
• Further evaluated using bioavailability tools
 In-situ pore water metal concentrations
 Chemical analyses of whole body and fillets of pelagic fish
species
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Remedial Design and Implementation
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Risk mitigation, reduction, or removal is ultimate goal of
every remedial action
If bioavailability indicates adverse impact to receptors,
then design the remedy accordingly
Bioavailability measurement tools can be used to monitor
effectiveness of remedy
Reduction in uncertainty
will enhance ability to evaluate
monitored natural recovery
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Limitations and Uncertainty
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There are uncertainties with data assessment methods
and models
Aquatic environments are dynamic, which may alter
physical, chemical and biological properties, and therefore
bioavailability factors, through time
Stakeholder interests and land usage at or surrounding a
site can change over time, thus shifting remedial priorities
Regulatory acceptance cannot be assumed
Just remember . . .
 Collect data that answers a question about the site
 Knowing your site and good communication is the key
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Contaminated Sediment Assessment
Approach
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Scoping Your Site….Chapter 2
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Site history - Due Diligence
Site boundaries (extent of
contamination)
Contaminants of potential
concern (COPC)
Conceptual site model
(CSM) – source, exposure
pathway/route, receptors,
space, time, fate &
transport
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Processes to Consider During
Scoping
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Physical
Bed Transport
Deposition/ Resuspension
Bioturbation
Advection/diffusion
Grain size COPC distribution
Burial
Temperature
Caution – Sediment are mixtures
Chemical
• Sorption/desorption
• Transformation/
degradation
• Geochemical (TOC,
salinity, pH, Redox)
•
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Biological
Uptake
Biotransformation
Bioaccumulation
Mode of action
Critical body burden
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Example Conceptual Site Model
Anacostia River
Permitted
Facility
Discharge
Urban
• Storm Water
Tributaries
• Sewer
• Water Treatment
Plant
• CSO
Tidal Mixing/
Potomac River
Surface Water
Flow
Direction
Volatilization
Uncharacterized
Point
Discharges
Precipitation
Non-Point
Surface
Run-off
Suspended
Dissolution
Particles
Bioaccumulation
Adsorption
Desorption Groundwater
Recharge
Resuspension
Deposition
Burial
Surface Sediment
Deep Sediment
Epifauna
Infauna
Erosion
Flow
Direction
Bed Load
Transport
Groundwater
Discharge
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Screening Your Site…Chapter 3

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Screening values (e.g. SQVs) are not site specific
Conservative values
• Levels below which there is a good probability there is low
risk
• Values above screening levels do not imply unacceptable
level of risk
Determine if there is a need for
further investigation
 Do not use as clean up levels/PRGs
Many SQVs have been established
 Beware – know how your
screening levels were derived!
(e.g. McDonald 2000 “consensus” values)

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Screening and Bioavailability


Normalization of bulk sediments (section 3.1.2.2) can
be applied within the screening process under some
state regulatory programs (e.g. TOC for PAHs/EqP;
iron, aluminum for metals)
However the assessment of site impacts is improved
by incorporating bioavailability in later stages of the
site investigation using site specific considerations
Source: NRC, 2003
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Specific Exposure Pathways
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Most Common Exposure Pathways
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Benthic Pathway…Chapter 4
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Procedures for Assessing Bioavailability
to Benthic Invertebrates

Sediment Quality Triad (SQT):
Chemistry
(bulk sediment
and pore water
concentration)
Toxicity
(solid phase;
extract/leachate;
bioaccumulation)
Biology
(macroinvertebrate abundance,
diversity, benthic indices,
body burden)
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Tools to Assess the Benthic Pathway;
Chemical - Sediment

SEM/AVS
• Simultaneously
Extracted Metals/
Acid Volatile
Sulfides

SEM-AVS/fOC
No Toxicity
Toxicity Uncertain
Toxicity Probable
From EPA-600-R-02-011, 2005
130
3000
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Tools to Assess the Benthic Pathway;
Chemical - Porewater

Porewater (Direct)
• Centrifugation (lab)
• Syringes/suction devices
• Piezometers
• Ultraseep/Trident probe
• SPME (solid phase
microextraction; EPA SW-846
8272; ASTM D73-63-07)

Porewater (Indirect)
• Peeper
• SPMD (semi-permeable
•
•
•
•
membrane device) / dialysis
bags
Diffusion in thin films (DGT)
SPME, POM
(Polyoxymethylene) film, PE
(Polyethylene) strips
GORE® Module
Diffusive flux
Surface Water
Oligochate
Sediment
Surface
Sediment
Particles
Porespace filled
with water
(porewater)
33
Tools to Assess the Benthic Pathway;
Chemical - Porewater (Direct) – Suction
Devices
Airstone “Before”
Airstone “After”
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Tools to Assess the Benthic Pathway;
Chemical - Porewater (Indirect) –
SPMD/Dialysis Bags
SPMD “Before”
SPMD “After”
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Tools to Assess the Benthic Pathway;
Chemical - Porewater (Indirect) – “Peepers”
Assembled
Sampler components
Clear
acrylic
body
Cell
Membrane
Lexane
wedge
Dialysis
Base plate membrane
Cover
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Tools to Assess the Benthic Pathway;
Chemical - Porewater (Indirect) – “Peepers”
Depth (cm)
40
Water
column
20
0
Black
ooze
-20
-40
Tan
medium
sand
-60
-80
0
Photographs courtesy of A.
Lee Gustafson, Net Zero LLC
1
2 3 4 5
Arsenic (mg/L)
South
Central
North
6
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Tools to Assess the Benthic Pathway;
Chemical - Porewater (Direct) – Trident
Probe and Ultraseep
Trident
Probe*
Ultraseep*
*http://www.oceanscience.com/pdf/ultraseep_trident.pdf
38
Tools to Assess the Benthic Pathway;
Chemical - Porewater (Direct/Indirect) –
SPME (Solid Phase Micro Extraction)
Syringe
Sample Vial
39
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Tools to Assess the Benthic Pathway;
Chemical - Porewater (Indirect) – GORE®
Module
Screening tool that can be used to sample porewater
Measure concentrations in
GORE lab only
Cord
Verified use in groundwater
attached to
To Surface
float or
Mainly effective for VOCs
insertion
probe
Multiple
sorbents
in sample
Water and
soil particles
remain outside
GORE-TEX
membrane
Organic
vapors
pass
through
40
Tools to Assess the Benthic Pathway;
Biological - Sediment Toxicity Tests
Neanthes
arenaceodentata
Hyalella azteca
FRESHWATER
BRACKISH OR
SALTWATER
Chironomus dilutus
Eohaustorius estuarius
41
Tools to Assess the Benthic Pathway;
Biological - Macroinvertebrate Surveys
“Pollution Sensitive”
“Pollution Tolerant”
Benthic Metrics: Abundance, Richness, %EPT, %Dominance,
%Chironomids, Hilsenhoff’s or Shannon-Weiner Diversity Indices
42
Tools to Assess the Benthic Pathway;
Biological - Minimally Disturbed Stream
Photos courtesy of Susan
Davies, Maine DEP
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Tools to Assess the Benthic Pathway;
Biological - Stream Adjacent to Shopping
Mall
Photos courtesy of Susan
Davies, Maine DEP
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Tools to Assess the Benthic Pathway
Predictive
Sediment – Pore Water Exposure
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Equilibrium partitioning
Narcosis model
SEM-AVS/fOC
Biotic ligand model
Biota
Sediment
Carbon
Ca2+
Na+
H
Competing Cations
Biotic Ligand Model
Organic Matter
Complexation
Equilibrium partitioning
M-Biotic
Ligand
M2+
M-DOC
Pore
Water
Free
Metal
+ Ion
Site of Action
MOH
MHCO3+
MCl+
Inorganic Ligand Complexation
Tipping, 1994
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Case Study Using the Benthic Pathway
Tectronix Wetlands Beaverton, OR

Historic operations → sediment metals
exceeding Oregon Department of
Environmental Quality (DEQ) Level II
screening level values
• Assessed chemistry, toxicity, SEM/AVS,TOC
 Maximum (SEM-AVS)/foc was ~10 less
than EPA’s adverse effect level
• Toxicity tests
 Hyalella azteca mortality
 Chironomus dilutus growth
 No adverse effect on amphipods or midges


Assessment concluded concentrations did not
pose potential risks to benthic community
NFA for stretch of Beaverton Creek based on
• Results from bulk sediment chemistry
• Toxicity testing
• Comparison to (∑SEM-AVS)/fOC toxicity
threshold
Photo courtesy
Kathleen Hurley
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Questions & Answers
47
Fish and Water Column
Invertebrates Pathway…Chapter 5
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Tools to Assess the Fish and Water
Column Invertebrates Pathway Chemical
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Measure water quality above sediment bed → compare to
• National recommended water quality concentration
• State water quality standards
Measure water and tissue residues → compare to
• Bioaccumulation Factors (BAF)
• Critical Body Burden (CBB): ~2.5 umol/g wet weight
• Toxicity Reference Values (TRV)
Measure Biota-sediment accumulation factors (BSAFs) =
[COPCtissue/flipid] / [COPCsed/fOC]
• <1 or >1?
49
Tools to Assess the Fish and Water
Column Invertebrates Pathway Biological



Conduct sediment toxicity tests using appropriate
organisms and conditions
Measure in situ bioavailability from field-collected
organisms
Conduct population surveys → compare to
“reference” conditions
50
Tools to Assess the Fish and Water
Column Invertebrates Pathway Predictive

Accumulation factors
• Bioconcentration factors
 USEPA EPISuite
• Bioaccumulation factors
 Public domain
 Peer-reviewed literature
• Biota-sediment accumulation factors
 e.g. U.S. Army Corp of Eng or ORD BSAF Dbase
• Biomagnification factors

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Biotic ligand model (metals)
Food web models
51
Case Study Using the Fish and Water
Column Invertebrates Pathway
McCormick and Baxter Superfund Site, OR



Residual creosote-derived contaminants including PAHs and dioxins
Assessments
• Sediment chemistry
• Bioassays
• Tissue residues in fish and crayfish
• Fish histopathology
Results
• Sediment chemistry and toxicity testing
 Indicated area of the Willamette River - likely to be toxic
• Tissue residues for PAHs were low in
 Crayfish (Pacifastacus leniusculus)
 Large scale sucker (Catastomus macrocheilus)
 Examination of 249 fish livers found no statistical differences
between the site and upstream locations

ROD required placement of an impermeable cap, based on
• Sediment chemistry and bioassay data
• Continuing NAPL discharges from sediments to Willamette River
52
Wildlife Pathway…Chapter 6
53
Tools to Assess the Wildlife Pathway:
Indirect Measures

Wildlife effects
(already known)
• Bulk sediment
(mg/kg)
• Literature BAFs
• Percent of diet




Freshwater (Mallard)
Saltwater (Sandpiper)
Calculate: dose (mg/kg/day)
Compare: to threshold reference value (TRV)
Pass?
• Yes → NFA
• No → SLERA/BERA
Exposure/effect:
bioaccessibility in
sediment
Dose (mg/kg/day) = % Sediment (in diet)
CSED (mg/kg) x %diet (kg/day) = mg/kg/day
Tools to Assess the Wildlife Pathway;
Indirect Measures
logW-PBET gizzard Pb
(mg kg-1)
54
4
3
2
1
0
0
1
2
3
4
5
6
7
Blood Pb
(mg kg-1, wet weight)
Photo courtesy of Nick Basta, Soil &
Envir. Chemistry, Ohio State Univ.
Furman et al., J. Environ. Qual. 35: p.
450 https://www.soils.org/publications/
jeq/articles/36/3/899
55
Tools to Assess the Wildlife Pathway;
Direct Measures

Tissue residue analysis
• Need clear endpoints

Toxicity testing
• Expensive but sitespecific

Food web modeling
• Simple vs. complex

Population surveys
13.8 ppm
Tertiary
consumers
2.07 ppm
Secondary
consumers
0.23 ppm
Primary
consumers
0.04 ppm
Producers
• Consider scale vs.
home range
56
Plants Pathway…Chapter 7
57
Tools to Assess the Plants Pathway


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Bioassay (e.g. seedlings)
Bioaccumulation (vegetative)
Plant toxicity (e.g. boron)
58
Human Health Pathway…Chapter 8
59
Exposure in Human Health Pathway

Direct contact with sediment
• Ingestion
• Dermal contact

Consumption
• Fish
• Wildlife
• Plant
Incidental
Sediment
Ingestion
Fish & Wildlife
Ingestion
Water
Fowl
Fish
Aquatic
Surface Water
Vegetation Benthic
Pore
Organisms Water
Soil/Groundwater
Sediment
60
Direct Contact

Preliminary screening
• Compare bulk sediment concentrations to human healthbased soil screening levels (SSLs)

Refine screening levels
• Modify exposure variables
• Modify bioavailability assumptions
 Adherence of sediments to skin
 Dermal absorption efficiency
 Gastrointestinal absorption efficiency
61
Human Consumption of Fish and
Shellfish

Contaminants of concern
• Primarily concerned with bioaccumulative constituents
• In general bioaccumulation concerns should be limited to
select classes of organics (pesticides, PCBs, dioxins) and
mercury

Adjust screening levels
• Contaminant concentration available in sediment pore water
(Section 4)
• Site specific conditions such as TOC or fish lipid fraction

Direct tissue analysis
62
Human Consumption of Fish and
Shellfish

Adjust screening levels
– example (Text Box 8-1)
• Recreational human fisherman screening level =
0.019 mg/kg for hexachlorobenzene (HCB)
 Default values for fish lipid fraction = 0.03
 Sediment fraction organic carbon (foc) = 0.01
• Site-specific screening level = 0.28 mg/kg
 Used site-specific fish lipid fraction of 0.02 and foc
of 0.10
• Applying site-specific information raises screening
value 15x
63
Human Consumption of Wildlife and
Plants

Wildlife
• Incidental ingestion of sediment, aquatic
vegetation and benthic and/or pelagic organisms
• Obtain information on dietary habits of species of
concern
• Addressed in Chapter 6

Plants
• Grown in contaminated area (e.g. seaweed, wild
rice) or crops in dredge spoils
• Tissue sampling to determine COPCs
• Addressed in Chapter 7
64


Case Study – Industri-plex Superfund
Site
Once nation’s leading producer of lead
arsenate
2-step study of arsenic in river sediments
• Step 1 – Narrow focus for live tests
 In vitro test on river sediments from four
areas
 Sediments in reactor that simulates the
stomach fluid of humans
• Step 2 – Test relative bioavailability to
humans
 Tested two sets of river sediment materials
 Immature swine fed dough balls with
sediment test materials
 RBA of the site sediments were 37% and
51%, respectively

Study reduced the estimated human health risk
in half
65
Case Study Using Bioavailability
Indiana Steel and Wire Site - Mocks Pond
66
Site Description and Background


Galvanizing plant, Muncie, Indiana
2.8 acre former limestone quarry
• Received plant production wastewater from
1962-1973
• Lime was added to neutralize wastewater before
discharge to pond
• Pond contained 51,000 cubic yards of stabilized
spent pickling sludge
• Sediment samples contained high concentrations
 Heavy metals (Sb, As, Cd, Cr, Cu, Pb, and Zn)
 Cyanide
67
Site Characterization Efforts

Sediment and surface water investigations
• Sediment toxicity and leachability studies (1980’s)
• Waste characterization study (1993)
• Standard bulk chemistry sediment and surface
water sampling for metals and cyanide (1999)

Biological assessment
• Water column properties assessment including
plankton type
• Macroinvertebrate and
fish surveys
• Fish tissue sampling for
metals and cyanide
• Wildlife surveys
68
Site Characterization Results:
Surface Water and Sediment




Physical nature of the sludge not conducive to benthic
organisms
• Fine grained
• No organic matter/nutrients
Neutralization of the wastewater discharge with lime
forming insoluble metal hydroxides suggested lack of
metals bioavailability
Preliminary surface water sampling results in compliance
with water quality standards
Sediment results exceed sediment screening criteria
(SSC)
Concentration
SSC
Cr
21 - 2,100 ppm
120 ppm
Cu
150 - 6,210 ppm
100 ppm
Pb
201 - 8,000 ppm
82 ppm
69
Site Characterization Results:
Biological Assessment

Healthy populations
• Present
 Pelagic fish
 Phytoplankton
 Zooplankton species
• Absent
 Benthic fish
 Macroinvertebrates
70
Bioavailability Investigation Activities:
Human Health Risk Assessment





Screened sediment and fish data
• Indiana Tier II residential cleanup goals for soil
• EPA Region III Residential RBCs for fish tissue
COPECs in sediment: Sb, Cr, Pb and Zn
Fish tissue: As
Exposure routes
• Incidental ingestion
• Dermal contact
• Ingestion of fish
Receptors
• Future construction workers
• Park worker and recreational visitors
• Anglers
71
Bioavailability Investigation Activities:
Human Health Risk Assessment (continued)

Used exposure modeling to determine risk
• IEUBK model for Pb
• Intake modeling for other metals
Conclusion: Remediation of pond sediment is necessary to address direct
contact issues with Pb in sediment to the future construction worker and
ingestion of arsenic in fish tissue for future recreational anglers.
72
Bioavailability Investigation Activities:
Ecological Risk Assessment

Screened sediment and fish tissue data
• Sediment criteria
 Assessment and Remediation of Contaminated
Sediments (ARCS) Program for the Great Lakes
Threshold Effects Levels (TELs)
 Lowest Effects Levels (LELs) (Persuad, 1993)
 Washington State Lowest
Apparent Effects
Thresholds (LAETs)
• Fish tissue criteria
 Compared to background
concentrations from
White River
73
Bioavailability Investigation Activities:
Ecological Risk Assessment (continued)

Sediment COPCs
• Sb, As, Cd, Cr, Cu, Pb, Hg,

Ni, Ag, Zn and cyanide

Fish tissue COPCs
• None (concentrations less
than background)

Exposure routes
• Incidental ingestion
• Dermal contact
• Ingestion of fish

Receptors
• Benthic invertebrate
• Piscivorous birds
• Piscivorous mammals
Used dietary exposure
modeling to determine risk to
higher trophic level
organisms
Conclusion: Considerable level of risk exist to benthic
organisms, benthic fish and submerged and emergent
aquatic macrophytes from sediment exposures due to
levels of metals in sediment and the absence of these
feeding guilds in the pond
74
Remedial Design: Sediment
Excavation and Capping




Dredging sediment to clear water depth of 10 feet
Placement of a geotextile fabric liner followed by
a subaqueous fine to medium grain sand cap
atop the residual sediment
Post-construction monitoring
(borings/bathymetry)
Five years of annual post-remedial monitoring to
evaluate cap performance in restricting the
migration of constituents into the biotic zone
75
5 Year Post-Remedial Monitoring and
Bioavailability Testing



5 Year Annual Monitoring Plan
Pore water sampling to evaluate cap performance
• In situ sampling via large diameter peepers
• Inserted 10 centimeters into the sediment
Surface water sampling to assess
functional effects on the water
column community
Sediment sampling to confirm
isolation of metal contamination
76
Post-Remedial Monitoring/
Bioavailability Investigation Findings


Post-Construction Monitoring Results
Cap performed in accordance with design
• Uniformly overlies pond bottom
• Physically stable
• Effectively isolating the residual underlying sediment
5 Yr Annual Monitoring Results
Sediment, surface water and pore water quality met
site-specific standards
• Metals tightly sequestered
• Metals not biologically available
77
Sediment Quality Improvements and
Case Study Summary
Initial
Post-Remedial
Concentration Concentrations
Range (1999)
(at 5th Year)
Sediment
Cleanup
Standard
Constituent
(mg/kg)
(mg/kg)
(mg/kg)
Antimony
36 to 315
0.034 to 0.11B
64
Arsenic
8.9 to 18
2.2 to 6.7
48
Cadmium
1.3 to 12
0.13 to 0.39
3.2
Chromium
21 to 2,100
ND
120
Copper
150 to 6,210
5.9 to 80.4
100
Lead
201 to 8,000
4.6 to 63.8
82
78
Overall Course Summary

Bioavailability should be an
integral part of characterization
and remedial decision making

Bioavailability can be assessed
throughout the process but is
more justifiable after the initial
screening process

Bioavailability will help you refine
your exposure results and refine
your risk management decisions
Current ITRC project:
• Remedial Decision-making at
Contaminated Sediment Sites
79
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
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
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
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