9.1.3 Data Requirements

9.1.3 Data Requirements

The evaluation of plant bioaccumulation requires information on the CDF and

its environmental setting, the planned dredged material management, and the

characteristics of the dredged material, as well as information on animal ROC

populations outside the CDF from Chapter 8. Much of this comes from the

available information complied in Tier I, supplemented (if necessary) by the

Tier II and Tier III test data.

9.1.4 Summary of Tiered Evaluation of Plant Bioaccumulation

The other contaminant mobility pathways addressed in the UTM are evaluated

primarily on the basis of standards or criteria, and risk assessment plays a

relatively minor role in Tiers I through III. In the absence of technically

applicable standards or criteria, plant (and animal) bioaccumulation evaluations in

the UTM rely more directly on risk assessment in Tiers I through III. Evaluation

of all pathways relies on risk assessment in Tier IV.

The risk-based approach to evaluation of plant bioaccumulation is structured

around the conceptual site model developed in Tier I. The conceptual site model

provides the framework and the context for conducting the evaluation (Cura,

Wickwire, and McArlde in preparation). It describes the dredged material

management planned, the environmental setting of the site, and how the planned

site management interacts with the environmental setting to determine what

effects might potentially occur. The evaluation in Tiers I through III emphasizes

three components evaluated in the context of the conceptual site model:

Receptors of concern (ROC), discussed in Section 2.2.3. These are

animal populations off the site.

Constituents or contaminants of concern (COC), discussed in Sections

2.2.2 and 3.4.

Complete exposure routes, discussed in Section 3.2.4. Identification of

reasonable complete exposure routes by which ROC can come into direct

physiological contact with COC is key to the entire evaluation. If there

are no reasonable complete exposure routes, there can be no exposure and

thus no effect or risk.

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. Identification of complete exposure routes (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.

9-3

Chapter 9

Plant Bioaccumulation