What is Risk Assessment?

assessment. Subsequent sections describe how these two categories of risk

assessment differ.

Risk assessment in its more common manifestations is an often used, although

not necessarily formally recognized, component of the dredged material

management decision-making process. For example, Peddicord et al. (1997) note

that the present procedure for evaluating water column impacts in dredged material

evaluations (USEPA/USACE 1991, 1998) is an application of ecological risk

assessment.

In its most basic form, risk assessment means answering several simple

questions which usually underlie dredged material management decisions. These

include:

a. Are there humans, organisms, or habitats (all called receptors) near the

proposed dredged material management activities?

b. Are there chemicals or physical hazards associated with the proposed

dredged material which may affect the survival or reproduction of these

receptors? The answer to this question is called a hazard identification.

c. Is there a known quantity of the chemical or physical hazard which results

in an adverse effect to the likely receptors? This is called toxicity

assessment or effects assessment.

d. Are there any conservative, but realistic, activities or physical and

biological pathways by which the receptors may encounter the chemical or

physical hazards associated with a particular proposed dredged material

activity? This is termed exposure assessment.

e. Finally, under a specified set of conditions, will this encounter result in an

exposure to the chemical or physical hazard at a level known to cause an

adverse effect? (Risk characterization).

Generally, if the answer to this last question is no, then we assume that the risk

associated with the dredged material management decision is acceptable. If it is yes,

then there is some potential unacceptable risk, and we begin to search for ways to

modify management activities or receptor activities to lower the exposure and hence

risk. The decision maker asks one additional question:

f. How confident are we in our answer? (Uncertainty analysis).

Viewed as a formal approach to answering these simple and commonly posed

questions, risk assessment appears as a familiar thought process. Also, dredged

material managers and USACE field operations personnel will recognize that the

information necessary to answer these questions is nearly always available from

data developed as part of the site selection process and tiered evaluation process

described in the Dredged Material Testing Manuals (USEPA/USACE 1991, 1998).

Chapter 1 Overview of Ecological and Human Health Risk