Dredging/Dredged Material Management Risk Assessment

Technical Note DOER-R1

September 1998

Dredging/Dredged Material

Management Risk Assessment

PURPOSE: This technical note explains the use of risk assessment to facilitate dredged material

management decision-making in navigable waterways by U.S. Army Corps of Engineer (USACE)

project managers and field operations personnel. The document does not promote risk assessment

as a tool for use in every dredged material management decision. It is likely to be most useful, and

most used, in those cases that constitute the exception rather than the rule. The use of risk assessment

is intended to supplement the analytical options currently available to dredged material managers

by building on the existing technical framework (U.S. Environmental Protection Agency

(USEPA)/USACE 1992) and the existing tiered approaches (USEPA/USACE 1991, 1998).

BACKGROUND: Scientific advancements have made possible the collection of large amounts

of complex information regarding the environmental aspects of dredging and dredged material

disposal. The dredged material manager must often use "best professional judgement" to weigh

multiple and sometimes conflicting lines of evidence to reach a decision. Environmental risk

assessment provides a stepwise framework for the integration of complex information to yield

quantifiable estimates of risk including uncertainty. In addition, risk assessment allows the dredged

material manager to make explicit the types of information considered and how a decision is reached

regarding the suitability of a dredged material for a particular management option.

INTRODUCTION: This document describes the general components of risk assessment; provides

an overview of the risk assessment option as applied to the dredged material management process;

and describes various technical documents being prepared or planned to help the USACE field

operations staff implement the risk assessment option.

RISK ASSESSMENT: Often, and contrary to a USEPA directive to be transparent, discussion

of risk assessment is obscured with technical jargon and "terms of art." This document attempts to

provide nontechnical definitions for such terms and emphasizes the initial use of the term in bold

italics.

What is a risk assessment? Risk assessment is the process of evaluating the impact of a

stressor (e.g., a chemical or physical condition) upon the health of individual humans or the

environmental well being of a population or community of animals and plants. The former is called

human health risk assessment, and the latter ecological risk 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.