9.5.2 Tier IV - Plant Bioaccumulation Decision

By the nature of the tiered evaluation approach, any technical questions that

remain unresolved after Tier III can best be answered by a detailed, case-specific

evaluation. By their very nature, detailed, case-specific evaluations are not

amenable to the kind of generic guidance that can be presented in a national

manual. They require individual design to address unique technical questions

under site-specific conditions.

The best approach for Tier IV is usually a case-specific risk assessment.

Detailed guidance for conducting risk assessments for CDFs in Tier IV can be

found in Cura, Wickwire, and McArlde (in preparation). The information

generated in Tiers I through III should be used to the maximum extent technically

justified throughout the Tier IV risk assessment.

9.5.2 Tier IV - Plant Bioaccumulation Decision

After consideration of the Tier IV evaluation results, all relevant information

is available and no further evaluation is possible. One of the following

conclusions is reached.

1. No management actions are required.

2. Management actions should be considered. A decision to implement

management actions for plant bioaccumulation by interrupting complete

exposure routes to ROC populations outside the CDF may require more

detailed information prior to design of such actions.

9.5.3 Plant Bioaccumulation Management Actions

When there is concern about the potential for effects related to plant

bioaccumulation, management actions related to the design, operation, and

management of the CDF may be considered. In general, anything that interrupts a

complete exposure route to ROC populations outside the CDF may act as an

effective control of plant bioaccumulation. Therefore, the evaluation that

identifies complete exposure routes will often also provide ideas for management

actions that interrupt them. Additional information on management actions and

references for detailed guidance on such actions are found in Chapter 10 of this

manual.

9.6 References

Cura, J., Wickwire, T., and McArlde, M. "Ecological and human health risk

assessment guidance for terrestrial environments," DOER Technical Report

(in preparation), U.S. Army Engineer Research and Development Center,

Vicksburg, MS.

Folsom, B. L., Jr., Lee, C. R., and Bates, D. J. (1981). "Influence of disposal

environment on availability and plant uptake of heavy metals in dredged

9-12

Chapter 9

Plant Bioaccumulation