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Page Title: Step 4: Specify contaminants of concern (Cont.)
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d. Criteria for protection of humans from consumption of water and
organisms.
Those compounds which meet WQC and are neither bioaccumulatable nor act
synergistically with other compounds will be screened out as COCs. The risk
assessment can screen out compounds which do or may bioaccumulate if their Tier
II analyses of TBP in the dredged sediments is less than the TBP calculated for
reference sediments. If the TBP for the dredged sediment is greater than the TBP for
reference sediments according to Tier II protocols, then the decision to retain or
screen out the COC depends on the results of Tier III testing.
Summary of Tier III evaluations. Tier III assesses the impact of contaminants in
the dredged material on appropriate sensitive organisms to determine if there is a
potential for the dredged material to have an unacceptable impact. This tier uses
water-column and whole sediment toxicity bioassays and bioaccumulation tests.
Water-column toxicity bioassays assess the effects of sediment-associated
contaminants on water-column organisms. Water-column toxicity tests must be used
when WQC are not available or when synergistic effects are suspected. If the
concentrations of dissolved plus suspended contaminants do not exceed 0.01 of the
acutely toxic concentrations, the dredged material complies with water-column
toxicity criteria. If the concentration exceeds 0.01 of the acutely toxic
concentrations, the dredged material does not comply.
Whole sediment bioassays assess the effects of sediment-associated
contaminants on benthic organisms. If bioassay organism mortality is statistically
greater than in the reference sediment and exceeds mortality in the reference
sediment by at least 10 percent (or a value that is in accordance with approved
testing methods), the dredged material does not meet the limiting permissible
concentration for benthic toxicity.
Tier III benthic bioaccumulation tests determine bioavailability through 28-day
exposure tests. Bioaccumulation potential has to be in compliance with regulations
before a dredged material can be considered acceptable for ocean dumping. Tier III
includes comparing concentrations of COCs in tissues of benthic organisms after a
28-day exposure period to Food and Drug Administration (FDA) Action Levels. It
is considered unacceptable if the concentration of contaminants in any test species
exceeds FDA action levels.
If tissue contaminant concentrations are less than FDA action levels or if no
FDA levels are available, they must be compared to contaminant concentrations in
tissues of organisms similarly exposed to reference sediment. If tissue
concentrations of COCs in organisms exposed to dredged material do not
statistically exceed those of organisms exposed to reference sediment, then the
dredged material complies with bioaccumulation regulations. If the concentrations
of COCs in organisms exposed to dredged material exceed those of organisms
exposed to reference sediment, Tier III provides eight factors to consider to
determine compliance.
Application of Tier III results to selection of contaminants of concern. The
selection of COCs for the risk assessment uses the Tier III bioaccumulation test
29
Chapter 2 Problem Formulation

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