When should the project manager consider applying risk assessment?

Technical Note DOER-R1

September 1998

ecological receptor may encounter contaminants or a physical disturbance associated with the

dredged material option. For example, a state agency may express a specific concern regarding

how a management alternative may affect people who fish near the dredged material management

site. The risk assessment can then address this concern by developing an exposure scenario with a

recreational fisherman using the nearby waters and catching and eating fish with a specific

Risk assessment is distinct from risk management. The National Academy of Sciences (National

Research Council 1983) defines risk management as "the process of weighing policy alternatives

and selecting the most appropriate regulatory action, integrating the results of risk assessment with

engineering data and with social, economic, and political concerns to reach a decision." Under this

definition, risk management should reflect local and contemporary concerns and value judgements.

However, risk assessment is more objective, focusing upon several end points (measurable

characteristics of an ecological or human receptor that may be affected by exposure to a physical

stress or contaminant) and estimating risk in reference to these. Once the end points are established,

the risk assessment proceeds without modification to them. One can change the assumptions of risk

assessment regarding technology, exposure scenarios, or site characteristics, but the risk estimate

is always the result of comparing exposure to receptors with these fixed, previously established end

points.

The risk assessment avoids problems associated with simple statistical comparison to a reference

sediment. For example, a dredged material evaluation may indicate that the proposed dredged

material has statistically higher bioaccumulation than a reference sediment. However, this does not

necessarily mean that the test sediment has a significantly higher toxicological effect. The risk

assessment puts the estimate of risk into a broader context that considers the potential for effect in

light of a measured toxicological response for a specific chemical under a set of site-specific

conditions.

The assumptions of any risk assessment should be clearly stated (USEPA 1992). Statements

regarding uncertainty associated with the assumptions should be included, and if possible, the effect

of changing the assumptions over some reasonable range should be demonstrated.

A risk assessment for a specific site and project provides "value added" because it is, with

modification, easily applicable to other projects at the same site. From project to project the dredged

material evaluation may change, but the data from the site selection report remain constant.

Therefore, the risk manager, by substituting the project-specific dredged material evaluation data,

can use the same risk assessment scenarios at a site with multiple projects over several years. The

entire assessment does not have to be reengineered with each new project. However, the assessment

will require additional field data to account for accumulative effects associated with multiple

projects.

When should the project manager consider applying risk assessment? The project

manager should decide to apply a risk assessment within the context of the site selection process

and/or the tiered evaluation of dredged material, or when there are unresolved issues with regard to

potential human or ecological exposures. Risk assessment is not separate from the current methods