9.1.2 Regulatory Considerations

manual provide a basis for determining if bioaccumulation in plants poses a risk

of effects on populations of receptors of concern outside the CDF.

The UTM is concerned only with effects outside the CDF. Therefore, in the

UTM plant bioaccumulation is of concern only if it is part of a complete exposure

pathway from the dredged material to animals that live outside the CDF and feed

(either as herbivores or predators of herbivores) on plants that bioaccumulate

COC from the dredged material in the CDF.

To illustrate the concept, in the context of the UTM there is typically not a

concern about COC.

Bioaccumulation by:

Unless:

Terrestrial plants

A bird flies in from offsite and eats the the plant

in a CDF

(geese eat tubers and leaves)

Aquatic plants in

A person catches and eats a fish from aquatic

a CDF

habitats within the CDF that feeds on herbivorous

aquatic invertebrates

A fox comes onto the site and eats a herbivorous

Wetland plants in

a CDF

rodent

Because the concern in the UTM is for potential effects outside the site,

bioaccumulation is considered a component of exposure for off-site ROC, and is

not evaluated as an indicator of potential effects on the on-site plants that may

accumulate the COC directly from the dredged material. Unlike the other

contaminant mobility pathways addressed in the UTM, there are presently no

standards or criteria that can be directly applied in a technically sound manner to

plant (or animal) bioaccumulation. Therefore, plant bioaccumulation from

dredged material in a CDF is evaluated on the basis of its potential to cause effects

on animal populations outside the site (Section 2.2.4).

The first step in determination of the potential for effects is to compare

bioaccumulation from the dredged material to that from a properly selected

reference material. If bioaccumulation from the dredged material is not

statistically greater than that from the reference material, bioaccumulation is not

considered to pose a potential for effects. If bioaccumulation from the dredged

material is statistically greater than from the reference material, further evaluation

in subsequent tiers is necessary to determine the potential for effects. Because the

reference material is carefully selected to represent acceptable conditions,

whatever bioaccumulation it may cause is an acceptable level of plant

bioaccumulation. Although statistical significance, per se, cannot indicate

environmental importance, a statistically significant increase above reference

bioaccumulation has been considered in the OTM and ITM to indicate a potential

for effects, and that convention is followed in the Tiers II and III plant

bioaccumulation in the UTM. Detailed decision guidance is provided in the

discussions of each of the tiers.

9-2

Chapter 9

Plant Bioaccumulation