Example 4: Identifying Contaminants of Concern

For the marina project under consideration, five contaminants found in the dredging material intended for

the offshore management site met the criteria for Tier I identification of COCs. Specifically, cadmium,

lead, mercury, endosulfan, and PCBs are potential contaminants of concern because they are present in

the material and have known toxicological effects.

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 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.

Acute

Saltwater

Criteria for

Protection of

Predicted

COCs

Criterion

Human Water

Health

Contaminant

Retained

Contaminant

Criterion

Chronic Conc.

Conc. (ug/L)

and

Organisms

Concentration

Organisms

Only

(ug/L)

Cadmium

9.3

10.4

Endosulfan

0.034

0.0087

159

0.0067

Lead

220

8.5

14.7

Mercury

2.1

0.025

0.146

0.14

0.019

PCBs

0.03

7.90E-05

1.2

NA = Not available

Reference:

USEPA (1999). National recommended water quality criteria. USEPA, Office of Water, Washington,

DC. EPA/822-Z-99-001.

Figure 4. Identification of Contaminants of Concern

Chapter 2 Problem Formulation