8.2.1 Compilation and Evaluation of Existing Information

dredged material characteristics are unchanged, new evaluations may not be

necessary.

8.2.1 Compilation and Evaluation of Existing Information

The Tier I information generated in Chapter 3 is the technical basis for the Tier I

evaluation of animal bioaccumulation. Because the Tier I animal (and plant)

bioaccumulation evaluation relies more heavily on a risk assessment approach than

the evaluation of the other pathways, the Tier I information from Chapter 3 is

organized and used in a risk assessment framework. The information compiled and

used in Chapter 3 to identify relevant contaminant mobility pathways is organized

and used as described below to develop a conceptual site model specific to the

project being evaluated. The information from Chapter 3 on COC and ROC is

evaluated in the context of the conceptual site model. The Tier I animal

bioaccumulation evaluation emphasizes identification of complete exposure routes

in the context of the conceptual site model. There can be no risk unless there is a

complete exposure route by which an ROC can come into direct physiological

contact with a COC.

8.2.2 Development of Conceptual Site Model

Guidance on development of a conceptual site model is available in Cura,

Wickwire, and McArlde (in preparation), from which this section, specific to

evaluation of animal bioaccumulation, is summarized. The conceptual site model

for evaluation of animal bioaccumulation is an integration of existing information

which identifies the COC and their sources, describes the exposure routes

involving animal bioaccumulation by which they may reach ecological and human

ROC, and specifies which ecological and human ROC might be linked to the

COC by these routes. The conceptual site model is a narrative or diagram that

describes the links between COC and ROC along explicit fate and transport routes

involving animal bioaccumulation.

The conceptual model is the basis for determining which fate and transport

processes involving animal bioaccumulation will be examined, deciding which

receptors to address, and identifying the COC that will be evaluated. In order to

evaluate risks, it is important to clearly identify all three elements: the stressors,

the receptors, and the exposure routes that connect them. The absence of a

complete exposure route is one basis for early elimination of some exposure

routes and stressor/receptor sets from further consideration in a risk assessment, so

that the process can focus on situations that might reasonably constitute a potential

risk. This is the opportunity to focus questions upon issues of real concern.

Because the conceptual model is so fundamental to the conduct and acceptance of

the risk assessment, it is important that Federal and State agencies, interested

parties, and the general public have meaningful participation in the development

of the conceptual model.

8-6

Chapter 8

Animal Bioaccumulation