8.2.2 Development of Conceptual Site Model (Cont.)

common ecological descriptions of terrestrial or aquatic habitats. The

habitat classifications should not be so broad as to lose ecological

meaning, nor so specific that they lack information regarding the

relationships among organisms. The product of this step is narrative text,

maps, and figures, as necessary, which describe the habitats at and

adjacent to the CDF.

3. Identify the off-site animal species and humans that may consume animals

that have bioaccumulated COC from the dredged material at present and

under reasonably foreseeable future conditions. To identify ecological

ROC, first identify nearby biological communities as general types such

as riverine, forest, or meadow/grassland. Then list the animals of various

types and feeding habits that are likely to be important within these

general communities and to consume animals that have taken up COC

from the dredged material. The ecological ROC should reflect the variety

of trophic levels, feeding types, and phylogenetic diversity in the

identified habitats. The product is a list (generally three to eight are

sufficient) of ecological ROC that may, now and within the reasonably

foreseeable future, consume animals that have taken up COC from the

dredged material. The list describes the role each ROC plays at the site

and how they represent other species of similar feeding types, etc. It also

briefly describes why other species at the site were not selected as ROC.

4. Specify the COC for animal bioaccumulation. The goals are to focus on

those constituents that warrant detailed evaluation, and document the

reasons others do not warrant further consideration, resulting in a focused

list of COC necessary and sufficient for a thorough assessment of risks

associated with animal bioaccumulation for the project being evaluated.

Simple presence of a constituent in the dredged material being evaluated

is not sufficient to include that constituent as a potential COC. The

primary factors to consider in identifying COC for animal

bioaccumulation include frequency of presence in the dredged material,

concentration in the dredged material relative to the concentration in the

reference material, toxicological importance, persistence in the

environment and propensity to bioaccumulate in animals. The product is

a site-specific list of COC, documenting why each was retained, and why

other constituents were not considered COC.

5. Describe mechanisms that may bring COC into contact with a human or

ecological ROC. This step in a risk assessment is essentially the same as

the identification of relevant contaminant mobility pathways, completed

in Section 3.2, which showed animal bioaccumulation warrants

evaluation for the project in question. The product of this step is a

narrative that describes how animal bioaccumulation of COC from the

dredged material could reach animals living outside the CDF.

6. Describe the potential processes of contact between COC and ROC. The

simple existence of a mechanism that may transport a COC to a ROC will

not result in a complete exposure route unless there is some process by

which the COC comes into actual physiological contact with a ROC.

8-8

Chapter 8

Animal Bioaccumulation