Is risk assessment a proved approach to aid decision-making?

Technical Note DOER-R1

September 1998

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

underlie dredged material management decisions:

Are humans, organisms, or habitats (all called receptors) near the proposed dredged material

management activities?

Are chemicals or physical hazards that may affect the survival or reproduction of these

receptors associated with the proposed dredged material? The answer to this question is called

a Hazard Identification.

Is there a known quantity of the chemical or physical hazard that results in an adverse effect

to the likely receptors? This is called Toxicity Assessment or Effects Assessment.

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.

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 Charac-

terization)?

Generally, if the answer to this last question is no, then the risk associated with the dredged

material management decision is assumed to be 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:

How confident are we in our answer (Uncertainty Analysis)?

Viewed as a formal approach to answering these simple, 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).

A risk assessment is essentially complete when it provides defensible answers to these 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 USACE (e.g., ADDAMS) with one of several biological food chain models

available in the scientific literature. USACE is preparing a series of technical documents that will

guide managers and operations personnel in the appropriate application of these models. USACE

is also developing a series of technical guidance and support documents and on-line databases to

support field operations personnel in conducting risk assessment.

Is risk assessment a proved approach to aid decision-making? The USACE personnel

who may use the risk assessment option should recognize that risk assessment is not new or

unplowed ground. A prior USACE publication (USACE 1995) noted that risk assessment has a

long history in business (e.g., financial risk, insurance industry, cost/benefit analyses), health care

(evaluation of drug efficiency versus side effects, efficacy of treatment), and government.