2.2.1 Overview of Risk Assessment

conditions expected as a result of the proposed project. The UTM

processes of scoping the technical evaluation and identification of

relevant COC migration pathway(s) discussed in Section 3.1 is generally

analogous to this step of the risk assessment process.

Effects assessment determines the dose-response that might cause an

effect, such as exceedence of a water quality standard or an effect

resulting from bioaccumulation. Effects assessment characterizes the

dredged material and is independent of the CDF. The evaluations

conducted in Tiers I through III concerning releases or impacts of the

contaminant migration pathways in Chapters 4 through 9 are generally

analogous to this step of the risk assessment process.

Exposure assessment determines the conditions of exposure to COC that

populations, communities, or ecosystems would experience in the field as

a result of the proposed project. Exposure assessment characterizes

conditions in the field related to the project and is independent of the

effects assessment. The mixing, dispersion, or attenuation of effluent,

runoff, leachate and volatiles, and the exposure conditions to entire

dredged material in Tiers I through III of the contaminant migration

pathways in Chapters 4 through 9 are one aspect of exposure assessment.

The exposure evaluation should also consider exposure times in relation

to the times implicit in the measurements of effects. Exposure evaluation

should consider the spatial scale of the release in relation to the scale of

the receiving water body and the distribution of the ROC at the

population level and in relation to potential ecosystem effects. The

considerations discussed in Section 2.2.4 are an important part of

exposure evaluation.

Risk characterization basically involves comparison of the results of the

effects assessment and exposure assessment to determine whether there is

a risk. If conditions necessary to cause an effect (effects assessment) are

greater than the exposure expected in the field (exposure assessment),

there is no risk. However, if exposure conditions are greater than those

that will cause effects, a potential risk exists. The evaluation and decision

processes in Tiers I through III of the pathways in Chapters 4 through 9

are generally analogous to this step of the risk assessment process.

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Chapter 2 Structure and Approach of the UTM