Proper Timing for Risk Assessment

A risk assessment is essentially complete when it provides defensible answers to

the above questions. Current Federal, state, and industry guidance recognizes that

risk assessment can be a fairly simple set of answers to these questions. The level of

effort needed ranges from a simple "back of the envelope" calculation to something

as sophisticated as integrating the various fate and transport models available from

U.S. Army Engineer Waterways Experiment Station (WES) (e.g., ADDAMS. See

USACE 1995a) with one of several biological food chain models available in the

scientific literature. The Corps is preparing a series of technical documents which

will guide managers and operations personnel in the appropriate application of these

models. The Corps is also developing a series of technical guidance and support

documents and on-line databases to support field operations personnel in conducting

risk assessment.

Proper Timing for 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 of

decision-making. It merely enhances them.

A formal assessment is not something to be applied to every project. It is most

applicable to projects which have:

a. Reached Tier IV and concern about specific bioaccumulative compounds or

toxic compounds remains.

b. The potential to affect a local sensitive habitat or species.

c. Outstanding exposure issues where a risk assessment will allow realistic

use of information about a species' natural history such as foraging areas,

breeding times, migration patterns.

d. Potential human health exposure either directly to sediments or through the

food chain.

e. Issues associated with environmental windows.

Risk assessment is not applied to the typical dredged material site or project

which is easily handled through the existing technical framework. Rather, it applies

in those cases where an extended analysis allows the dredged material manager to

address such real-world conditions as sediment matrix effects, bioavailability,

intermittent use of the site by a species of concern, the mitigating effects of a

specific management technology, the likely exposure to people fishing

recreationally, etc.

Chapter 1 Overview of Ecological and Human Health Risk