Step 7: Describe complete exposure routes

resuspended sediments in energetic environments). In shallow waters, there may be

exposure via plant uptake and subsequent herbivores. In the figure, the terms

"primary receptor" and "secondary receptor" represent general trophic levels, not a

prioritization of importance. Note that this conceptual model depicts a shallow site

where forage fish and zooplankton are important receptors and are important

biological media for exposure to higher trophic levels (groundfish and pelagic fish).

Contaminant exposure pathways that do not lead to a species or group of species

or humans which may be potential receptors are incomplete and therefore the risk

assessor may assume that there is no potential for risk associated with a particular

contaminant along that pathway (Figure 3).

The product of Steps 6 and 7 is a graphical and narrative description of the

complete exposure routes specific for the COCs, habitats, types of species, and

likely human receptors. It should include a written summary of the chemical,

physical, and biological conditions at the proposed disposal site. Where data are

insufficient to conduct any of the preceding steps, the description should recommend

means (e.g., field surveys) to provide the information necessary to complete the

conceptual model. In those cases where further field or laboratory work is

recommended, the description should also stipulate the required data goals and

methodology. Subsequent steps in the ecological risk assessment, particularly the

development of a list of receptors, will depend on the site characterization inherent

in the development of the conceptual model.

Chapter 2 Problem Formulation