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 Table 1 (Continued)
Uncertainty
Ease with Which
Type of
Magnitude of
and/or
Uncertainty Can
Uncertainty2
Uncertainty4
Variability1
Be Quantified?3
Uncertainty Source
Tier IV Evaluation: Chronic Bioassays
Chronic Bioassays
u,v
Model
Easy
Low
Precision of bioassay
Interpretation of bioassay
u,v
Model
Moderate
Moderate
Tier IV: Human Health and Ecological Risk Assessments Problem Formulation/Hazard Identification
Characterization of Dredged Material - see Tier I
Development of Conceptual Model
Characterization of the surrounding environment
u,v
Scenario
Difficult
NR
u
Scenario
Difficult
PS
Identification of complete and incomplete pathways
Selection of potential receptors
u
Scenario
Difficult
PS
Assessment and Measurement End Points
u
Scenario
Difficult
NR
Selecting assessment end points
Selecting measurement end points
u
Scenario
Difficult
PS
Exposure Assessment
Estimation of Exposure Point Concentrations
Fate and transport models: model uncertainty
u,v
Model
MS
MS
Fate and transport models: parameter uncertainty
u
Parameter
Difficult
Moderate
Physical and chemical properties of COCs (Kow, Koc, Kdoc)
Physical and chemical properties of COCs (vapor pressure, molecular weight, solubility)
u
Parameter
Moderate
Low
Bioaccumulation of COCs
u,v
Model
Easy
Moderate
Bioavailability from sediments for ecological receptors
Bioavailability from water for ecological receptors
u,v
Model
Moderate
Moderate
u,v
Model
Easy
Low
Exposure models for aquatic organisms: equilibrium models
u,v
Model
Easy
MS
Use of equilibrium models when time-variant models are more appropriate
Parameter uncertainty (uptake, elimination, and growth rates, etc.)
u,v
Parameter
Moderate
Moderate
u,v
Model
Moderate
MS
Exposure models for semiaquatic organisms and humans: model uncertainty
u,v
Model
Easy
Moderate
Exposure models for semiaquatic organisms and humans: parameter uncertainty
Physiological characteristics (e.g., body weight, inhalation rate, etc.)
v
Parameter
Easy
Low
u,v
Scenario
Moderate
Moderate
Exposure duration (migration, foraging area, feeding patterns)
u,v
Parameter
Easy
Low
Time-activity patterns for workers involved in dredging and disposal activities
(Sheet 2 of 3)
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