8.2 Tier I Initial Evaluation of Animal Bioaccumulation

Tier I involves many activities essential to the entire evaluation. It includes

compilation of available information, construction of a conceptual site model,

development of initial COC, identification of ROC, and identification of complete

exposure routes to populations of animal ROC off the site. Identification of

complete exposure routes to off-site animal ROC populations (and by implication,

those potential exposure routes that are not complete and thus pose no risk) is a

major emphasis of Tier I. Tier I also includes evaluation of the available

information to reach a decision about the acceptability of any COC/ROC/exposure

pathway combinations for which there is sufficient information for a decision and

identify the remaining COC for further evaluation in subsequent tiers.

If a decision about the need for management actions based on animal

bioaccumulation cannot be reached based on existing information in Tier I, the

evaluation may be carried to Tier II. Tier II consists of evaluation of the

theoretical bioaccumulation potential (TBP) of nonpolar organic COC. Those

COC for which the results indicate little potential for bioaccumulation may be

eliminated with regard to animal bioaccumulation, and those for which further

information is necessary to reach a decision may be carried to Tier III.

Tier III consists of laboratory bioaccumulation tests for the remaining COC

using surrogate species. Those COC for which the results indicate little potential

for bioaccumulation may be eliminated with regard to animal bioaccumulation,

and those for which further information is necessary to reach a decision may be

carried to Tier IV.

The evaluations of Tiers I through III will be sufficient to reach a decision

about most COC in most cases. In those situations where this is not the case, a

full risk assessment of the remaining COC may be conducted in Tier IV.

The procedures in the various tiers can be applied to evaluate the performance

of existing CDFs and to design new sites. For existing sites, the techniques can be

used to predict the potential for bioaccumulation for a given set of anticipated opera-

tional conditions (e.g., CDF size). In a similar manner, the required operational

conditions for a new site (e.g., frequency of new lifts) to avoid bioaccumulation can

be determined by comparing the predicted bioaccumulation for a variety of assumed

operational conditions. In either case, evaluation of bioaccumulation must be

considered in conjunction with a sound design of the CDF for retention of

suspended solids and initial storage of the sediments to be dredged.

8.2 Tier I Initial Evaluation of Animal

Bioaccumulation

Animal bioaccumulation is evaluated only if the Tier I evaluation of the

proposed project (Chapter 3) demonstrates that contaminant evaluations are needed

and that animal bioaccumulation is a contaminant mobility pathway of concern for

the project. It is important to consider prior evaluations of the animal

bioaccumulation pathway to determine if additional evaluations are needed. For

example, if prior tests or evaluations are available, and project conditions and

8-5

Chapter 8

Animal Bioaccumulation