Dredging Scenario

consumption to the receptor intake model. The MEPAS human health impacts module estimates

health impacts from inhalation, ingestion, or dermal contacts as either cancer incidences or hazard

index as appropriate for the contaminant of concern.

Dredging Scenario. The dredging scenario includes the processes associated with the short-term

disturbance caused by the dredging action as well as the processes present in the no-action

alternative. Dredging impacts are limited to those associated with the loss of solids and associated

contaminants from the dredging operation. The scenario does not include the effects of the physical

disturbance or entrainment by the dredge on the organisms. The resuspended material will be

transported from the dredging site and dispersed in a plume. The size of the plume where significant

increases in contaminant concentrations occur is usually small and may not include the entire depth

of the water column. Contaminants from the resuspended material will distribute between the water

and solids phases. Solids from the resuspended material plume will settle and deposit on the bottom,

changing the contaminant concentration in the surficial sediments. Significant deposition occurs

only in the immediate vicinity of the dredge, and the effects of deposition are generally small.

The conceptual model for the dredging scenario is shown in Figure 9. The sources of the

contaminants are resuspended material, sediment, and water column. Interactions between the