Uncertainty in Tiered Evaluation of Dredged Material

Uncertainty in Tiered

Evaluation of Dredged Material

This section outlines important sources of uncertainty in the evaluation of

potential environmental impacts of dredged material disposal. Uncertainty

sources are discussed within the USACE/USEPA tiered evaluation structure

(Figure 1).

TIER I

EVALUATE

(Generally

EXISTING

represents existing

INFORMATION

information)

WATER

SEDIMENT

COLUMN

MEASURE AND MODEL

CALCULATE THEORETICAL

DISSOLVED CONTAMINANTS

BIOACCUMULATION

Compare to surface water

POTENTIAL

TIER II

quality standards

Compare to reference

TIER III

MEASURE TOXICITY

Model suspended phase

Solid phase tests

(Generic bioassay

Determine toxicity after

Measure bioaccumulation

tests for toxicity

mixing

and compare to Food &

and

Drug Administration (FDA)

bioaccumulation)

limits and to reference

CONDUCT CASE-SPECIFIC

CASE-SPECIFIC TOXICITY

TOXICITY TESTS

TIER IV

Bioaccumulation tests

(Specific

Other tests

bioassay tests,

Risk assessment

risk assessment)

Figure 1.

USACE/USEPA tiered evaluation of dredged material for disposal (after ITM

(USEPA/USACE 1998))

Chapter 4 Uncertainty in Tiered Evaluation of Dredged Material