Ecological Exposure Assessment, Effects Assessment, and Risk Characterization

Ecological Exposure

Assessment, Effects

Assessment, and Risk

Characterization

Exposure Assessment

An ecological exposure assessment builds upon the qualitative descriptions in

the conceptual model to calculate a quantitative estimate of the exposure of selected

receptors to the COC. As described in Chapter 2, the selection of COCs depends on

information from the sediment evaluation procedures, and the conceptual model

identifies the potential exposure pathways. The goals of the exposure assessment

are to:

a. Calculate the physical movement of the contaminants of concern from the

disposal site to the point where they may come into contact with a receptor.

b. Provide a concentration of the contaminant of concern at that point.

c. Estimate how much of the contaminant may be ingested or otherwise

absorbed into the body of the receptor.

The ecological exposure has three general steps (Figure 7):

Step 1: Estimating the concentration of COCs in the dredged

material

This step attempts to provide a conservative estimate of the initial concentra-tion

to use in any further calculations or modeling of contaminant movement or transfer

through a food chain. This calculation begins with an estimate of the con-centration

of the contaminant at the disposal site.

The assessment should use the upper 95th-percent confidence limit on the arith-

metic mean of the concentration of each COC to represent the projected concen-

tration at the disposal site based on its EPA guidance. Where the data set is

Chapter 3 Ecological Exposure Assessment