Description of Complete Exposure Pathways

the water during placement. The area is a low-to-moderate energy environment,

has a seasonal thermocline (indicating little surface to bottom mixing during

summer), and is generally depositional. There is some potential for resuspension

of the sediments and advection through wave or storm action and during winter

with the breakdown of the seasonal thermocline. There is also potential for

diffusion from pore water and advection offsite. These mechanisms could bring

the potential COCs into contact with receptors.

Description of Complete Exposure Pathways

The risk assessor used the following questions to guide the determination of

complete exposure pathways between the proposed dredged material and the

potential receptors:

a. Could contaminants reach receptors via direct contact?

b. Are one or more receptors inhabiting or using an area where

contamination exists or will exist?

c. Is the location of contamination such that one or more receptors could

contact it currently or in the future?

d. Are there advective or dispersive processes which may deliver the

contaminant to a receptor or habitat?

e. Could contaminants reach receptors via indirect contact?

f. Is contamination bioaccumulative or bioconcentratable?

g. Are there higher-order predators which may accumulate the

contaminant?

h. Could contaminants reach receptors or habitats via groundwater?

i. Can contaminants leach into groundwater?

j. Does groundwater discharge to aquatic habitats? Are contaminants

present at surface sediments?

k. Can contaminants be leached or eroded from surface sediments or soil?

The answers to these questions indicate that there is a benthic community

with potential for direct contact and ingestion of sediments by invertebrate

organisms at the management area. There is then potential for bioaccumulation to

higher-order predators through ingestion of the benthic organisms. There is some

potential for bioconcentration of COCs from suspended sediments in the water

column to forage fish and zooplankton, given the moderate vertical mixing which

may occur at the site in winter. The management option does not have an effluent

discharge, so there is minimal likelihood of dissolved contamination in the water

column (there is a potential for exposure in the water column during disposal, but

Appendix F Hypothetical Example