8.2.3 Tier I - Evaluation Procedure

These processes may include dermal contact, ingestion, or inhalation.

The product should (1) specify the likely contact process(s) for each

ROC separately, and (2) document those processes that, even though they

may be part of complete exposure routes, are sufficiently minor to not

warrant further attention.

7. Describe the complete exposure routes, and eliminate from further

evaluation those potential routes that are not complete. This step

describes each complete exposure route in detail, including the identity

and source of each COC, the release mechanism, the process of exposure

and the activities of the ROC that bring it into direct physiological contact

with the COC. A complete exposure route is a combination of physical,

chemical, and biological processes that bring a COC from dredged

material into direct physiological contact with an ecological (e.g., a bird)

or a human (e.g., fisherman) ROC. Potential exposure routes that are

incomplete should be documented and not considered further. A

complete exposure route does not necessarily translate to risk. Risk

depends on the concentration or dose of COC to the ROC relative to that

receptor's toxic response. The exposure assessment component of the risk

assessment will address issues regarding the dose or concentration of

COC to which a ROC is likely to be exposed in the field, and the effects

assessment component addresses the levels at which the COC has the

potential to adversely affect the receptor. The product of Steps 6 and 7 is

a graphical and narrative description of the complete exposure routes

specific for the COCs, habitats, and ecological and human ROC. It is a

written summary of the chemical, physical, and biological conditions at

the CDF.

Where data are insufficient to fully develop a complete conceptual site model,

the site model should be developed as completely as possible, using clearly

identified assumptions and estimations where necessary. As the evaluation

progresses through the tiers, these assumptions and estimations may be replaced

with more definitive information as it becomes available.

8.2.3 Tier I - Evaluation Procedure

A fundamental emphasis of the Tier I evaluation is on identification of

complete exposure routes to ROC outside the CDF. Complete exposure routes are

evaluated in Tier I if the available information is sufficient to make a decision,

and if there is not sufficient information to support a decision, they are carried to

subsequent tiers for more detailed evaluation. Incomplete exposure routes to

ROC outside the CDF, and complete routes that clearly involve such minimal

potential exposure as to pose negligible risk of unacceptable adverse effect, are

documented and eliminated from further consideration.

A key to the evaluation of ecological impacts of animal bioaccumulation in

Tier I, as well as in subsequent tiers, is the concept of effect as discussed in

Section 2.2.4. Effects are generally evaluated at the population or higher level

rather than at the level of individual organisms, except in the case of endangered

8-9

Chapter 8

Animal Bioaccumulation