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Page Title:
Description of Potential Release Mechanisms |
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 The tabulation below provides the WQC and the predicted concentrations for
the potential COCs from Tier II evaluations. The evaluation revealed that neither
lead nor cadmium have WQC for the protection of humans from consumption of
organisms. These two contaminants must, therefore, be retained as COCs.
The remaining contaminants, mercury, endosulfan, and PCBs, have all WQC
including: acute criteria for the protection of aquatic life; chronic criteria for the
protection of aquatic life; criteria for the protection of humans from organisms
only; and criteria for protection of humans from water and organisms. Among
these three potential contaminants, the predicted water concentration of total
PCBs from the dredged material exceeded the criteria. Therefore, total PCBs
were retained as a COC.
A theoretical bioaccumulation potential could not be calculated for mercury
because it is an inorganic compound. Therefore, a Tier III evaluation was
necessary to determine compliance. The Tier III evaluation revealed that
bioaccumulation of mercury in the dredged material was less than that of the
reference sediment, and it was screened out as a COC.
Because endosulfan is a nonpolar organic compound, a theoretical
bioaccumulation potential (TBP) could be calculated, but the TBP, in this case,
did not exceed that of the reference sediment. In addition, no synergism with
other potential COCs was suspected, and endosulfan was screened out as a COC.
At the end of the three-tiered evaluation, three contaminants in the dredged
material, cadmium, lead, and PCBs, were selected as contaminants of concern for
the risk assessment. This continuous example will carry total PCBs through the
risk assessment.
Saltwater
Saltwater
Criteria for
Protection of
Predicted
Criterion
Criterion
Human Water
Health
Contaminant
COCs
Acute Conc.
Chronic Conc.
and
Organisms
Contaminant
(ug/L)
(ug/L)
Organisms
Only
Concentration
Retained
Cadmium
43
9.3
10
NA
10.4
X
Endosulfan
0.034
0.0087
74
159
0.0067
Lead
220
8.5
50
NA
14.7
X
Mercury
2.1
0.025
0.146
0.14
0.019
PCBs
10
0.03
7.90E-05
7.90E-05
1.2
X
NA = Not available
Reference: USEPA (1999). "National recommended water quality criteria,", EPA/822-Z-99-001, Office of Water, Washington, DC.
Description of Potential Release Mechanisms
During this dredged material management operation, there are several
potential release mechanisms which could result in exposure to COCs. Once the
material has reached the management area, sediment can become suspended in
F4
Appendix F Hypothetical Example
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