Use of Numerical Effects Values

dredging project to another and from one region to another. It was suggested that

a pending site designation in the New England district could be used to

demonstrate the risk assessment process on a large-scale project. Ways to

distribute the cost of developing a risk assessment framework among stakeholders

were also discussed.

Participants noted the need for a demonstration project that would show

concerned stakeholders how risk assessment can be used in the decision-making

process. Participants also emphasized the need for having regulatory and

stakeholder acceptance for the use of realistic site-specific risk assessments, as

opposed to conservative screening-level assessments. Some members emphasized

that stakeholders should reach an early agreement on what, specifically, they are

trying to protect.

Several opinions were expressed concerning who would be responsible for

conducting risk assessments in the dredging program. In one scenario, Federal

employees would produce a model risk assessment for a particular site, perhaps as

part of the environmental impact statement (EIS) for the site. Modifications to the

model would be made in an assessment by the applicant, which would be reviewed

by Federal employees.

Use of Numerical Effects Values

Numerical effects values are concentrations of contaminants in sediment that

are expected to result in adverse effects on animals that inhabit the sediments.

Various approaches have been used to develop these values. The equilibrium

partitioning approach, which predicts effects of organic contaminants based on

organic carbon normalized sediment concentrations, has been used to develop

sediment quality action levels (USEPA 1993). Various empirical approaches are

based on empirical analyses of data compiled from bioassays of field-collected

samples, laboratory toxicity tests with spiked sediments, and benthic community

analyses (Long et al. 1995; Long, Field, and MacDonald 1998; USACE/USEPA

1989). The participants of the Effects Workgroup generally agreed that numerical

effects values should be used to constrain the assessment process, but no

consensus was reached on how the numbers should be used.

Some participants felt that numerical effects values could be used to "pass"

some sediments for open water disposal. For example, if managers and regulators

agree that the rate of false negatives for the Effects-Range approach (11 to

13 percent, Long et al. 1995; Long, Field, and MacDonald 1998) is acceptable,

the Effects-Range-Low (ERL) could be used to pass sediments. However, other

participants noted that these effects levels do not take into account the potential for

bioaccumulation and trophic transfer of contaminants. For example, some

persistent organic compounds are not acutely toxic to benthic invertebrates, but

are highly toxic to sensitive organisms at higher trophic levels.

Chapter 3 Effects Assessment Workgroup Summary